| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <SJ2PR11MB84724355C7C64FB98C098F34C9CDA@SJ2PR11MB8472.namprd11.prod.outlook.com>
Date: Thu, 13 Nov 2025 18:14:27 +0000
From: "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>, "hannes@...xchg.org"
<hannes@...xchg.org>, "yosry.ahmed@...ux.dev" <yosry.ahmed@...ux.dev>,
"nphamcs@...il.com" <nphamcs@...il.com>, "chengming.zhou@...ux.dev"
<chengming.zhou@...ux.dev>, "usamaarif642@...il.com"
<usamaarif642@...il.com>, "ryan.roberts@....com" <ryan.roberts@....com>,
"21cnbao@...il.com" <21cnbao@...il.com>, "ying.huang@...ux.alibaba.com"
<ying.huang@...ux.alibaba.com>, "akpm@...ux-foundation.org"
<akpm@...ux-foundation.org>, "senozhatsky@...omium.org"
<senozhatsky@...omium.org>, "sj@...nel.org" <sj@...nel.org>,
"kasong@...cent.com" <kasong@...cent.com>, "linux-crypto@...r.kernel.org"
<linux-crypto@...r.kernel.org>, "herbert@...dor.apana.org.au"
<herbert@...dor.apana.org.au>, "davem@...emloft.net" <davem@...emloft.net>,
"clabbe@...libre.com" <clabbe@...libre.com>, "ardb@...nel.org"
<ardb@...nel.org>, "ebiggers@...gle.com" <ebiggers@...gle.com>,
"surenb@...gle.com" <surenb@...gle.com>, "Accardi, Kristen C"
<kristen.c.accardi@...el.com>, "Gomes, Vinicius" <vinicius.gomes@...el.com>
CC: "Feghali, Wajdi K" <wajdi.k.feghali@...el.com>, "Gopal, Vinodh"
<vinodh.gopal@...el.com>, "Sridhar, Kanchana P"
<kanchana.p.sridhar@...el.com>
Subject: RE: [PATCH v13 00/22] zswap compression batching with optimized
iaa_crypto driver
> -----Original Message-----
> From: Sridhar, Kanchana P <kanchana.p.sridhar@...el.com>
> Sent: Tuesday, November 4, 2025 1:12 AM
> To: linux-kernel@...r.kernel.org; linux-mm@...ck.org;
> hannes@...xchg.org; yosry.ahmed@...ux.dev; nphamcs@...il.com;
> chengming.zhou@...ux.dev; usamaarif642@...il.com;
> ryan.roberts@....com; 21cnbao@...il.com;
> ying.huang@...ux.alibaba.com; akpm@...ux-foundation.org;
> senozhatsky@...omium.org; sj@...nel.org; kasong@...cent.com; linux-
> crypto@...r.kernel.org; herbert@...dor.apana.org.au;
> davem@...emloft.net; clabbe@...libre.com; ardb@...nel.org;
> ebiggers@...gle.com; surenb@...gle.com; Accardi, Kristen C
> <kristen.c.accardi@...el.com>; Gomes, Vinicius <vinicius.gomes@...el.com>
> Cc: Feghali, Wajdi K <wajdi.k.feghali@...el.com>; Gopal, Vinodh
> <vinodh.gopal@...el.com>; Sridhar, Kanchana P
> <kanchana.p.sridhar@...el.com>
> Subject: [PATCH v13 00/22] zswap compression batching with optimized
> iaa_crypto driver
>
> v13: zswap compression batching with optimized iaa_crypto driver
> ==============================================================
> ==
> This updated patch-series further generalizes the batching implementation of
> zswap_compress() for non-batching and batching compressors. It makes sure
> the
> bulk allocation of zswap entries preserves the current behavior of addition of
> an entry to the LRU list for the nid of the page.
>
> Based on Herbert's suggestions, the batching interfaces from zswap to crypto,
> from crypto to iaa_crypto, and the batching implementation within iaa_crypto
> now
> use the folio directly as the source (sg_page_iter for retrieving pages), and
> destination SG lists. A unit_size has been added to struct acomp_req, with
> kernel users such as zswap using the new acomp_request_set_unit_size() API
> to
> set the unit size to use while breaking down the request's src/dst
> scatterlists. zswap sets the unit-size to PAGE_SIZE.
Hi Nhat, Yosry, Herbert,
I just wanted to follow up on whether there are other code review comments
or suggestions you have on this latest patch set. Thanks very much for your time
in reviewing and improving the patch-series.
Nhat, I will make the change to the struct zswap_entry bit-fields to be
macro-defined constants, either as an update to this series, or submit a separate
patch with this change if that's Ok with you.
Thanks,
Kanchana
>
> Following Andrew's suggestion, the next two paragraphs emphasize
> generality and
> alignment with current kernel efforts.
>
> Architectural considerations for the zswap batching framework:
> ==============================================================
> We have designed the zswap batching framework to be hardware-agnostic. It
> has no
> dependencies on Intel-specific features and can be leveraged by any
> hardware
> accelerator or software-based compressor. In other words, the framework is
> open
> and inclusive by design.
>
> Other ongoing work that can use batching:
> =========================================
> This patch-series demonstrates the performance benefits of compress
> batching when used in zswap_store() of large folios. shrink_folio_list()
> "reclaim batching" of any-order folios is the next major work that uses
> this zswap compress batching framework: our testing of kernel_compilation
> with writeback and the zswap shrinker indicates 10X fewer pages get
> written back when we reclaim 32 folios as a batch, as compared to one
> folio at a time: this is with deflate-iaa and with zstd. We expect to
> submit a patch-series with this data and the resulting performance
> improvements shortly. Reclaim batching relieves memory pressure faster
> than reclaiming one folio at a time, hence alleviates the need to scan
> slab memory for writeback.
>
> Many thanks to Nhat for suggesting ideas on using batching with the
> ongoing kcompressd work, as well as beneficially using decompression
> batching & block IO batching to improve zswap writeback efficiency.
>
> Experiments with kernel compilation benchmark (allmod config) that
> combine zswap compress batching, reclaim batching, swapin_readahead()
> decompression batching of prefetched pages, and writeback batching show
> that 0 pages are written back to disk with deflate-iaa and zstd. For
> comparison, the baselines for these compressors see 200K-800K pages
> written to disk.
>
> To summarize, these are future clients of the batching framework:
>
> - shrink_folio_list() reclaim batching of multiple folios:
> Implemented, will submit patch-series.
> - zswap writeback with decompress batching:
> Implemented, will submit patch-series.
> - zram:
> Implemented, will submit patch-series.
> - kcompressd:
> Not yet implemented.
> - file systems:
> Not yet implemented.
> - swapin_readahead() decompression batching of prefetched pages:
> Implemented, will submit patch-series.
>
>
> iaa_crypto Driver Rearchitecting and Optimizations:
> ===================================================
>
> The most significant highlight of v13 is a new, lightweight and highly
> optimized iaa_crypto driver, resulting directly in the latency and
> throughput improvements noted later in this cover letter.
>
> 1) Better stability, more functionally versatile to support zswap
> with better performance on different Intel platforms.
>
> a) Patches 0002, 0005 and 0011 together resolve a race condition in
> mainline v6.15, reported from internal validation, when IAA
> wqs/devices are disabled while workloads are using IAA.
>
> b) Patch 0002 introduces a new architecture for mapping cores to
> IAAs based on packages instead of NUMA nodes, and generalizing
> how WQs are used: as package level shared resources for all
> same-package cores (default for compress WQs), or dedicated to
> mapped cores (default for decompress WQs). Further, users are
> able to configure multiple WQs and specify how many of those are
> for compress jobs only vs. decompress jobs only. sysfs iaa_crypto
> driver parameters can be used to change the default settings for
> performance tuning.
>
> c) idxd descriptor allocation moved from blocking to non-blocking
> with retry limits and mitigations if limits are exceeded.
>
> d) Code cleanup for readability and clearer code flow.
>
> e) Fixes IAA re-registration errors upon disabling/enabling IAA wqs
> and devices that exists in the mainline v6.15.
>
> f) Addition of a layer that encapsulates iaa_crypto's core functionality to
> rely only on idxd, dma and scatterlists to provide clean interfaces to
> crypto_acomp.
>
> g) New Dynamic compression mode for Granite Rapids to get better
> compression ratio by echo-ing 'deflate-iaa-dynamic' as the zswap
> compressor.
>
> h) New crypto_acomp API crypto_acomp_batch_size() that will return
> the driver's max batch size if the driver has registered a batch_size
> that's greater than 1; or 1 if there is no driver specific definition of
> batch_size.
>
> Accordingly, iaa_crypto sets the acomp_alg batch_size to its internal
> IAA_CRYPTO_MAX_BATCH_SIZE for fixed and dynamic modes.
>
> 2) Performance optimizations (please refer to the latency data per
> optimization in the commit logs):
>
> a) Distributing [de]compress jobs in round-robin manner to available
> IAAs on package.
>
> b) Replacing the compute-intensive iaa_wq_get()/iaa_wq_put() with a
> percpu_ref in struct iaa_wq, thereby eliminating acquiring a
> spinlock in the fast path, while using a combination of the
> iaa_crypto_enabled atomic with spinlocks in the slow path to
> ensure the compress/decompress code sees a consistent state of the
> wq tables.
>
> c) Directly call movdir64b for non-irq use cases, i.e., the most
> common usage. Avoid the overhead of irq-specific computes in
> idxd_submit_desc() to gain latency.
>
> d) Batching of compressions/decompressions using async submit-poll
> mechanism to derive the benefits of hardware parallelism.
>
> e) Batching compressors need to manage their own "requests"
> abstraction, and remove this driver-specific aspect from being
> managed by kernel users such as zswap. iaa_crypto maintains
> per-CPU "struct iaa_req **reqs" to submit multiple jobs to the
> hardware accelerator to run in parallel.
>
> f) Modifies the iaa_crypto batching API and their implementation to expect
> a
> src SG list that contains the batch's pages and a dst SG list that has
> multiple scatterlists for the batch's output buffers.
>
> g) Submit the two largest data buffers first for decompression
> batching, so that the longest running jobs get a head start,
> reducing latency for the batch.
>
> 3) Compress/decompress batching are implemented using SG lists as the
> batching
> interface.
>
>
> Main Changes in Zswap Compression Batching:
> ===========================================
>
> Note to zswap maintainers:
> --------------------------
> Patches 19 and 20 can be reviewed and improved/merged independently
> of this series, since they are zswap centric. These 2 patches help
> batching but the crypto_acomp_batch_size() from the iaa_crypto commits
> in this series is not a requirement, unlike patches 21-22.
>
> 1) v13 preserves the pool acomp_ctx resources creation/deletion
> simplification of v11, namely, lasting from pool creation-deletion,
> persisting through CPU hot[un]plug operations. Further, zswap no
> longer needs to create multiple "struct acomp_req" in the per-CPU
> acomp_ctx. zswap only needs to manage multiple "u8 **buffers".
>
> 2) We store the compressor's batch-size (@pool->compr_batch_size) directly
> in
> struct zswap_pool for quick retrieval in the zswap_store() fast path.
>
> 3) Optimizations to not cause regressions in software compressors with
> the introduction of the new unified zswap_compress() framework that
> implements compression batching for all compressors. These optimizations
> help recover the performance for non-batching compressors:
>
> a) kmem_cache_alloc_bulk(), kmem_cache_free_bulk() to allocate/free
> batch zswap_entry-s. These kmem_cache API allow allocator
> optimizations with internal locks for multiple allocations.
>
> b) The page's nid is stored in a new nid field added to zswap_entry, so the
> zswap_lru_add()/zswap_lru_del() will add/delete the entry from the LRU
> list of the page's nid. This preserves the current behavior wrt the
> shrinker.
>
> c) Writes to the zswap_entry right after it is allocated without
> modifying the publishing order. This avoids different code blocks
> in zswap_store_pages() having to bring the zswap_entries to the
> cache for writing, potentially evicting other working set
> structures, impacting performance.
>
> d) ZSWAP_MAX_BATCH_SIZE is used as the batch-size for software
> compressors, since this gives the best performance with zstd.
>
> e) Minimize branches in zswap_compress().
>
> 4) During pool creation, these key additions are allocated as part of the
> per-CPU acomp_ctx so as to recover performance with the new,
> generalized SG
> lists based zswap_compress() batching interface:
>
> a) An sg_table "acomp_ctx->sg_outputs" is allocated to contain the
> compressor's batch-size number of SG lists that will contain the
> destination buffers/lengths after batch compression.
>
> b) The per-CPU destination buffers are mapped to the per-CPU SG lists: this
> needs to be done only once, and optimizes performance.
>
> 5) A unified zswap_compress() API is added to compress multiple pages.
> Thanks
> to Nhat, Yosry and Johannes for their helpful suggestions to accomplish
> this.
>
> 6) Finally, zswap_compress() has been re-written to incorporate Herbert's
> suggestions to use source folios and output SG lists for batching. The new
> zswap_compress() code has been made as generic to software and batching
> compressors as possible, so that it is easy to read and maintain. The
> recent changes related to PAGE_SIZE dst buffers, zsmalloc and
> incompressible
> pages have been incorporated into the batched zswap_compress() as well.
> To
> resolve regressions with zstd, I took the liberty of not explicitly checking
> for dlen == 0 and dlen > PAGE_SIZE (as in the mainline); instead,
> expecting that a negative err value will be returned by the software
> compressor in such cases.
>
>
> Compression Batching:
> =====================
>
> This patch-series introduces batch compression of pages in large folios to
> improve zswap swapout latency. It preserves the existing zswap protocols
> for non-batching software compressors by calling crypto_acomp sequentially
> per page in the batch. Additionally, in support of hardware accelerators
> that can process a batch as an integral unit, the patch-series allows
> zswap to call crypto_acomp without API changes, for compressors
> that intrinsically support batching. The zswap_compress() code has very
> minimal
> special casing for software/batching compressors.
>
> The patch series provides a proof point by using the Intel Analytics
> Accelerator (IAA) for implementing the compress/decompress batching API
> using hardware parallelism in the iaa_crypto driver and another proof point
> with a sequential software compressor, zstd.
>
> SUMMARY:
> ========
>
> The first proof point is to test with IAA using a sequential call (fully
> synchronous, compress one page at a time) vs. a batching call (fully
> asynchronous, submit a batch to IAA for parallel compression, then poll for
> completion statuses).
>
> The performance testing data with 30 usemem processes/64K folios
> shows 62% throughput gains and 28% elapsed/sys time reductions with
> deflate-iaa; and 5% sys time reduction with zstd for a small
> throughput increase. For PMD folios, a 67% throughput gain and 23%
> elapsed/sys time reduction is seen.
>
> Kernel compilation test with 64K folios using 32 threads and the
> zswap shrinker_enabled set to "N", demonstrates similar
> improvements: zswap_store() large folios using IAA compress batching
> improves the workload performance by 3.5% and reduces sys time by
> 6% as compared to IAA sequential. For zstd, compress batching
> improves workload performance by 3.4% and reduces sys time by
> 1.8% as compared to sequentially calling zswap_compress() per page
> in a folio.
>
> The main takeaway from usemem, a workload that is mostly compression
> dominated (very few swapins) is that the higher the number of batches,
> such as with larger folios, the more the benefit of batching cost
> amortization, as shown by the PMD usemem data. This aligns well with the
> future direction for batching.
>
> The second proof point is to make sure that software algorithms such as
> zstd do not regress. The data indicates that for sequential software
> algorithms a performance gain is achieved.
>
> With the performance optimizations implemented in patches 21-22 of v13:
>
> * zstd usemem metrics with 64K folios are within range of variation
> with a slight sys time improvement. zstd usemem30 workload
> performance
> with PMD folios improves by 6% and sys time reduces by 8%, for
> comparable
> throughput as the baseline.
>
> * With kernel compilation, I used zstd without the zswap shrinker to enable
> more direct comparisons with the changes in this series. Subsequent
> patch
> series I expect to submit in collaboration with Nhat, will enable the
> zswap shrinker to quantify the benefits of decompression batching during
> writeback. With this series' compression batching within large folios, we
> get a 6%-1.8% reduction in sys time, a 3.5%-3.4% improvement in
> workload
> performance with 64K folios for deflate-iaa/zstd respectively.
>
> These optimizations pertain to ensuring common code paths and removing
> redundant branches/computes. Additionally, using the batching code for
> non-batching compressors to sequentially compress/store batches of up
> to ZSWAP_MAX_BATCH_SIZE pages seems to help, most likely due to
> cache locality of working set structures such as the array of
> zswap_entry-s for the batch.
>
> Our internal validation of zstd with the batching interface vs. IAA with
> the batching interface on Emerald Rapids has shown that IAA
> compress/decompress batching gives 21.3% more memory savings as
> compared
> to zstd, for 5% performance loss as compared to the baseline without any
> memory pressure. IAA batching demonstrates more than 2X the memory
> savings obtained by zstd at this 95% performance KPI.
> The compression ratio with IAA is 2.23, and with zstd 2.96. Even with
> this compression ratio deficit for IAA, batching is extremely
> beneficial. As we improve the compression ratio of the IAA accelerator,
> we expect to see even better memory savings with IAA as compared to
> software compressors.
>
>
> Batching Roadmap:
> =================
>
> 1) Compression batching within large folios (this series).
>
> 2) zswap writeback decompression batching:
>
> This is being co-developed with Nhat Pham, and shows promising
> results. We plan to submit an RFC shortly.
>
> 3) Reclaim batching of hybrid folios:
>
> We can expect to see even more significant performance and throughput
> improvements if we use the parallelism offered by IAA to do reclaim
> batching of 4K/large folios (really any-order folios), and using the
> zswap_store() high throughput compression pipeline to batch-compress
> pages comprising these folios, not just batching within large
> folios. This is the reclaim batching patch 13 in v1, which we expect
> to submit in a separate patch-series. As mentioned earlier, reclaim
> batching reduces the # of writeback pages by 10X for zstd and
> deflate-iaa.
>
> 4) swapin_readahead() decompression batching:
>
> We have developed a zswap load batching interface to be used
> for parallel decompression batching, using swapin_readahead().
>
> These capabilities are architected so as to be useful to zswap and
> zram. We have integrated these components with zram and expect to
> submit an
> RFC soon.
>
>
> v13 Performance Summary:
> ========================
>
> This is a performance testing summary of results with usemem30
> (30 usemem processes running in a cgroup limited at 150G, each trying to
> allocate 10G).
>
> usemem30 with 64K folios:
> =========================
>
> zswap shrinker_enabled = N.
>
> -----------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -----------------------------------------------------------------------
> zswap compressor deflate-iaa deflate-iaa IAA Batching
> vs.
> IAA Sequential
> -----------------------------------------------------------------------
> Total throughput (KB/s) 6,118,675 9,901,216 62%
> Average throughput (KB/s) 203,955 330,040 62%
> elapsed time (sec) 98.94 70.90 -28%
> sys time (sec) 2,379.29 1,686.18 -29%
> -----------------------------------------------------------------------
>
> -----------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -----------------------------------------------------------------------
> zswap compressor zstd zstd v13 zstd
> improvement
> -----------------------------------------------------------------------
> Total throughput (KB/s) 5,983,561 6,003,851 0.3%
> Average throughput (KB/s) 199,452 200,128 0.3%
> elapsed time (sec) 100.93 96.62 -4.3%
> sys time (sec) 2,532.49 2,395.83 -5%
> -----------------------------------------------------------------------
>
> usemem30 with 2M folios:
> ========================
>
> -----------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -----------------------------------------------------------------------
> zswap compressor deflate-iaa deflate-iaa IAA Batching
> vs.
> IAA Sequential
> -----------------------------------------------------------------------
> Total throughput (KB/s) 6,309,635 10,558,225 67%
> Average throughput (KB/s) 210,321 351,940 67%
> elapsed time (sec) 88.70 67.84 -24%
> sys time (sec) 2,059.83 1,581.07 -23%
> -----------------------------------------------------------------------
>
> -----------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -----------------------------------------------------------------------
> zswap compressor zstd zstd v13 zstd
> improvement
> -----------------------------------------------------------------------
> Total throughput (KB/s) 6,562,687 6,567,946 0.1%
> Average throughput (KB/s) 218,756 218,931 0.1%
> elapsed time (sec) 94.69 88.79 -6%
> sys time (sec) 2,253.97 2,083.43 -8%
> -----------------------------------------------------------------------
>
>
> This is a performance testing summary of results with
> kernel_compilation test (allmod config, 32 cores, cgroup limited to 2G).
>
> zswap shrinker_enabled = N.
>
> kernel_compilation with 64K folios:
> ===================================
>
> --------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> --------------------------------------------------------------------------
> zswap compressor deflate-iaa deflate-iaa IAA Batching
> vs.
> IAA Sequential
> --------------------------------------------------------------------------
> real_sec 836.64 806.94 -3.5%
> sys_sec 3,897.57 3,661.83 -6%
> --------------------------------------------------------------------------
>
> --------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> --------------------------------------------------------------------------
> zswap compressor zstd zstd Improvement
> --------------------------------------------------------------------------
> real_sec 880.62 850.41 -3.4%
> sys_sec 5,171.90 5,076.51 -1.8%
> --------------------------------------------------------------------------
>
>
> kernel_compilation with PMD folios:
> ===================================
>
> --------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> --------------------------------------------------------------------------
> zswap compressor deflate-iaa deflate-iaa IAA Batching
> vs.
> IAA Sequential
> --------------------------------------------------------------------------
> real_sec 818.48 779.67 -4.7%
> sys_sec 4,226.52 4,245.18 0.4%
> --------------------------------------------------------------------------
>
> --------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> --------------------------------------------------------------------------
> zswap compressor zstd zstd Improvement
> --------------------------------------------------------------------------
> real_sec 888.45 849.54 -4.4%
> sys_sec 5,866.72 5,847.17 -0.3%
> --------------------------------------------------------------------------
>
>
>
> The patch-series is organized as follows:
> =========================================
>
> 1) crypto acomp & iaa_crypto driver enablers for batching: Relevant
> patches are tagged with "crypto:" in the subject:
>
> Patch 1) Reorganizes the iaa_crypto driver code into logically related
> sections and avoids forward declarations, in order to facilitate
> subsequent iaa_crypto patches. This patch makes no
> functional changes.
>
> Patch 2) Makes an infrastructure change in the iaa_crypto driver
> to map IAA devices/work-queues to cores based on packages
> instead of NUMA nodes. This doesn't impact performance on
> the Sapphire Rapids system used for performance
> testing. However, this change fixes functional problems we
> found on Granite Rapids during internal validation, where the
> number of NUMA nodes is greater than the number of packages,
> which was resulting in over-utilization of some IAA devices
> and non-usage of other IAA devices as per the current NUMA
> based mapping infrastructure.
>
> This patch also develops a new architecture that
> generalizes how IAA device WQs are used. It enables
> designating IAA device WQs as either compress-only or
> decompress-only or generic. Once IAA device WQ types are
> thus defined, it also allows the configuration of whether
> device WQs will be shared by all cores on the package, or
> used only by "mapped cores" obtained by a simple allocation
> of available IAAs to cores on the package.
>
> As a result of the overhaul of wq_table definition,
> allocation and rebalancing, this patch eliminates
> duplication of device WQs in per-CPU wq_tables, thereby
> saving 140MiB on a 384 cores dual socket Granite Rapids server
> with 8 IAAs.
>
> Regardless of how the user has configured the WQs' usage,
> the next WQ to use is obtained through a direct look-up in
> per-CPU "cpu_comp_wqs" and "cpu_decomp_wqs" structures so
> as to minimize latency in the critical path driver compress
> and decompress routines.
>
> Patch 3) Code cleanup, consistency of function parameters.
>
> Patch 4) Makes a change to iaa_crypto driver's descriptor allocation,
> from blocking to non-blocking with retries/timeouts and
> mitigations in case of timeouts during compress/decompress
> ops. This prevents tasks getting blocked indefinitely, which
> was observed when testing 30 cores running workloads, with
> only 1 IAA enabled on Sapphire Rapids (out of 4). These
> timeouts are typically only encountered, and associated
> mitigations exercised, only in configurations with 1 IAA
> device shared by 30+ cores.
>
> Patch 5) Optimize iaa_wq refcounts using a percpu_ref instead of
> spinlocks and "int refcount".
>
> Patch 6) Code simplification and restructuring for understandability
> in core iaa_compress() and iaa_decompress() routines.
>
> Patch 7) Refactor hardware descriptor setup to their own procedures
> to reduce code clutter.
>
> Patch 8) Simplify and optimize job submission for the most commonly used
> non-irq async mode by directly calling movdir64b.
>
> Patch 9) Deprecate exporting symbols for adding IAA compression
> modes.
>
> Patch 10) All dma_map_sg() calls will pass in 1 for the nents instead of
> sg_nents(), for these main reasons: performance; no existing
> iaa_crypto use cases that allow multiple SG lists to be mapped for
> dma at once; facilitates new SG lists batching interface through
> crypto.
>
> Patch 11) Move iaa_crypto core functionality to a layer that relies only on
> the idxd driver, dma, and scatterlists. Implement clean interfaces
> to crypto_acomp.
>
> Patch 12) Define a unit_size in struct acomp_req to enable batching, and
> provides acomp_request_set_unit_size() for use by kernel
> modules. zswap_cpu_comp_prepare() calls this API to set the
> unit_size for zswap as PAGE_SIZE.
>
> Patch 13) Implement asynchronous descriptor submit and polling
> mechanisms,
> enablers for batching. Develop IAA batching of compressions and
> decompressions for deriving hardware parallelism.
>
> Patch 14) Enables the "async" mode, sets it as the default.
>
> Patch 15) Disables verify_compress by default.
>
> Patch 16) Decompress batching optimization: Find the two largest
> buffers in the batch and submit them first.
>
> Patch 17) Add a new Dynamic compression mode that can be used on
> Granite Rapids.
>
> Patch 18) Add a batch_size data member to struct acomp_alg and
> a crypto_acomp_batch_size() API that returns the compressor's
> batch-size, if it has defined one; 1 otherwise.
>
> 2) zswap modifications to enable compress batching in zswap_store()
> of large folios (including pmd-mappable folios):
>
> Patch 19) Simplifies the zswap_pool's per-CPU acomp_ctx resource
> management and lifetime to be from pool creation to pool
> deletion.
>
> Patch 20) Uses IS_ERR_OR_NULL() in zswap_cpu_comp_prepare() to check
> for
> valid acomp/req, thereby making it consistent with the resource
> de-allocation code.
>
> Patch 21) Defines a zswap-specific ZSWAP_MAX_BATCH_SIZE (currently set
> as 8U) to denote the maximum number of acomp_ctx batching
> resources to allocate, thus limiting the amount of extra
> memory used for batching. Further, the "struct
> crypto_acomp_ctx" is modified to contain multiple buffers.
> New "u8 compr_batch_size" member is added to "struct zswap_pool"
> to track the number of dst buffers associated with the compressor
> (more than 1 if the compressor supports batching).
>
> Modifies zswap_store() to store the folio in batches of
> pool->compr_batch_size (batching compressors) or
> ZSWAP_MAX_BATCH_SIZE (sequential compressors) by calling a new
> zswap_store_pages() that takes a range of indices in the folio to
> be stored.
>
> zswap_store_pages() bulk-allocates zswap entries for the batch,
> calls zswap_compress() for each page in this range, and stores
> the entries in xarray/LRU.
>
> Patch 22) Introduces a new unified batching implementation of
> zswap_compress() for compressors that do and do not support
> batching. This eliminates code duplication and facilitates
> code maintainability with the introduction of compress
> batching. Further, there are many optimizations to this common
> code that result in workload throughput and performance
> improvements with software compressors and hardware accelerators
> such as IAA.
>
> zstd performance is better or on par with mm-unstable. We
> see impressive throughput/performance improvements with
> IAA and workload performance/sys time improvement with zstd
> batching vs. no-batching.
>
>
> With v13 of this patch series, the IAA compress batching feature will be
> enabled seamlessly on Intel platforms that have IAA by selecting
> 'deflate-iaa' as the zswap compressor, and using the iaa_crypto 'async'
> sync_mode driver attribute (the default).
>
>
> System setup for testing:
> =========================
> Testing of this patch-series was done with mm-unstable as of 10-24-2025,
> commit 813c0fa931ce, without and with this patch-series. Data was
> gathered on an Intel Sapphire Rapids (SPR) server, dual-socket 56 cores
> per socket, 4 IAA devices per socket, each IAA has total 128 WQ entries,
> 503 GiB RAM and 525G SSD disk partition swap. Core frequency was fixed
> at 2500MHz.
>
> Other kernel configuration parameters:
>
> zswap compressor : zstd, deflate-iaa
> zswap allocator : zsmalloc
> vm.page-cluster : 0
>
> IAA "compression verification" is disabled and IAA is run in the async
> mode (the defaults with this series).
>
> I ran experiments with these workloads:
>
> 1) usemem 30 processes with zswap shrinker_enabled=N. Two sets of
> experiments, one with 64K folios, another with PMD folios.
>
> 2) Kernel compilation allmodconfig with 2G max memory, 32 threads, with
> zswap shrinker_enabled=N to test batching performance impact in
> isolation. Two sets of experiments, one with 64K folios, another with PMD
> folios.
>
> IAA configuration is done by a CLI: script is included at the end of the
> cover letter.
>
>
> Performance testing (usemem30):
> ===============================
> The vm-scalability "usemem" test was run in a cgroup whose memory.high
> was fixed at 150G. There is no swap limit set for the cgroup. 30 usemem
> processes were run, each allocating and writing 10G of memory, and
> sleeping for 10 sec before exiting:
>
> usemem --init-time -w -O -b 1 -s 10 -n 30 10g
> echo 0 > /sys/module/zswap/parameters/shrinker_enabled
>
> IAA WQ Configuration (script is iincluded at the end of the cover
> letter):
>
> ./enable_iaa.sh -d 4 -q 1
>
> This enables all 4 IAAs on the socket, and configures 1 WQ per IAA
> device, each containing 128 entries. The driver distributes compress
> jobs from each core to wqX.0 of all same-package IAAs in a
> round-robin manner. Decompress jobs are send to the wqX.0 of the
> mapped IAA device.
>
> Since usemem has significantly more swapouts than swapins, this
> configuration is the most optimal.
>
> 64K folios: usemem30: deflate-iaa:
> ==================================
>
> -------------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -------------------------------------------------------------------------------
> zswap compressor deflate-iaa deflate-iaa IAA Batching
> vs.
> IAA Sequential
> -------------------------------------------------------------------------------
> Total throughput (KB/s) 6,118,675 9,901,216 62%
> Avg throughput (KB/s) 203,955 330,040 62%
> elapsed time (sec) 98.94 70.90 -28%
> sys time (sec) 2,379.29 1,686.18 -29%
>
> -------------------------------------------------------------------------------
> memcg_high 1,263,467 1,404,068
> memcg_swap_fail 1,728 1,377
> 64kB_swpout_fallback 1,728 1,377
> zswpout 58,174,008 64,508,622
> zswpin 43 138
> pswpout 0 0
> pswpin 0 0
> ZSWPOUT-64kB 3,634,162 4,030,643
> SWPOUT-64kB 0 0
> pgmajfault 2,398 2,488
> zswap_reject_compress_fail 0 0
> zswap_reject_reclaim_fail 0 0
> IAA incompressible pages 0 0
> -------------------------------------------------------------------------------
>
>
> 2M folios: usemem30: deflate-iaa:
> =================================
>
> -------------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -------------------------------------------------------------------------------
> zswap compressor deflate-iaa deflate-iaa IAA Batching
> vs.
> IAA Sequential
> -------------------------------------------------------------------------------
> Total throughput (KB/s) 6,309,635 10,558,225 67%
> Avg throughput (KB/s) 210,321 351,940 67%
> elapsed time (sec) 88.70 67.84 -24%
> sys time (sec) 2,059.83 1,581.07 -23%
>
> -------------------------------------------------------------------------------
> memcg_high 116,246 125,218
> memcg_swap_fail 41 177
> thp_swpout_fallback 41 177
> zswpout 59,880,021 64,509,854
> zswpin 69 425
> pswpout 0 0
> pswpin 0 0
> ZSWPOUT-2048kB 116,912 125,822
> thp_swpout 0 0
> pgmajfault 2,408 4,026
> zswap_reject_compress_fail 0 0
> zswap_reject_reclaim_fail 0 0
> IAA incompressible pages 0 0
> -------------------------------------------------------------------------------
>
>
> 64K folios: usemem30: zstd:
> ===========================
>
> -------------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -------------------------------------------------------------------------------
> zswap compressor zstd zstd v13 zstd
> improvement
> -------------------------------------------------------------------------------
> Total throughput (KB/s) 5,983,561 6,003,851 0.3%
> Avg throughput (KB/s) 199,452 200,128 0.3%
> elapsed time (sec) 100.93 96.62 -4.3%
> sys time (sec) 2,532.49 2,395.83 -5%
>
> -------------------------------------------------------------------------------
> memcg_high 1,122,198 1,113,384
> memcg_swap_fail 192 55
> 64kB_swpout_fallback 192 55
> zswpout 48,766,907 48,799,863
> zswpin 89 68
> pswpout 0 0
> pswpin 0 0
> ZSWPOUT-64kB 3,047,702 3,049,908
> SWPOUT-64kB 0 0
> pgmajfault 2,428 2,390
> zswap_reject_compress_fail 0 0
> zswap_reject_reclaim_fail 0 0
> -------------------------------------------------------------------------------
>
>
> 2M folios: usemem30: zstd:
> ==========================
>
> -------------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -------------------------------------------------------------------------------
> zswap compressor zstd zstd v13 zstd
> improvement
> -------------------------------------------------------------------------------
> Total throughput (KB/s) 6,562,687 6,567,946 0.1%
> Avg throughput (KB/s) 218,756 218,931 0.1%
> elapsed time (sec) 94.69 88.79 -6%
> sys time (sec) 2,253.97 2,083.43 -8%
>
> --------------------------------------------------------------------------------
> memcg_high 92,709 92,686
> memcg_swap_fail 33 226
> thp_swpout_fallback 33 226
> zswpout 47,851,601 47,847,171
> zswpin 65 441
> pswpout 0 0
> pswpin 0 0
> ZSWPOUT-2048kB 93,427 93,238
> thp_swpout 0 0
> pgmajfault 2,382 2,767
> zswap_reject_compress_fail 0 0
> zswap_reject_reclaim_fail 0 0
> -------------------------------------------------------------------------------
>
>
> Performance testing (Kernel compilation, allmodconfig):
> =======================================================
>
> The experiments with kernel compilation test use 32 threads and build
> the "allmodconfig" that takes ~14 minutes, and has considerable
> swapout/swapin activity. The cgroup's memory.max is set to 2G. zswap
> writeback is not enabled so as to isolate the performance impact of only large
> folio batch compression.
>
> echo 0 > /sys/module/zswap/parameters/shrinker_enabled
>
> IAA WQ Configuration (script is at the end of the cover letter):
>
> ./enable_iaa.sh -d 4 -q 2
>
> This enables all 4 IAAs on the socket, and configures 2 WQs per IAA,
> each containing 64 entries. The driver sends decompresses to wqX.0 of
> the mapped IAA device, and distributes compresses to wqX.1 of all
> same-package IAAs in a round-robin manner.
>
> 64K folios: Kernel compilation/allmodconfig: deflate-iaa:
> =========================================================
>
> -------------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -------------------------------------------------------------------------------
> zswap compressor deflate-iaa deflate-iaa IAA Batching
> vs.
> IAA Sequential
> -------------------------------------------------------------------------------
> real_sec 836.64 806.94 -3.5%
> user_sec 15,702.26 15,695.13
> sys_sec 3,897.57 3,661.83 -6%
> -------------------------------------------------------------------------------
> Max_Res_Set_Size_KB 1,872,500 1,873,144
> -------------------------------------------------------------------------------
> memcg_high 0 0
> memcg_swap_fail 0 0
> 64kB_swpout_fallback 0 0
> zswpout 94,890,390 93,332,527
> zswpin 28,305,656 28,111,525
> pswpout 0 0
> pswpin 0 0
> ZSWPOUT-64kB 3,088,473 3,018,341
> SWPOUT-64kB 0 0
> pgmajfault 29,958,141 29,776,102
> zswap_reject_compress_fail 0 0
> zswap_reject_reclaim_fail 0 0
> IAA incompressible pages 684 442
> -------------------------------------------------------------------------------
>
>
> 2M folios: Kernel compilation/allmodconfig: deflate-iaa:
> ========================================================
>
> -------------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -------------------------------------------------------------------------------
> zswap compressor deflate-iaa deflate-iaa IAA Batching
> vs.
> IAA Sequential
> -------------------------------------------------------------------------------
> real_sec 818.48 779.67 -4.7%
> user_sec 15,798.78 15,807.93
> sys_sec 4,226.52 4,245.18 0.4%
> -------------------------------------------------------------------------------
> Max_Res_Set_Size_KB 1,871,096 1,871,100
> -------------------------------------------------------------------------------
> memcg_high 0 0
> memcg_swap_fail 0 0
> thp_swpout_fallback 0 0
> zswpout 105,675,621 109,930,550
> zswpin 36,537,688 38,205,575
> pswpout 0 0
> pswpin 0 0
> ZSWPOUT-2048kB 15,600 15,800
> thp_swpout 0 0
> pgmajfault 37,843,091 39,540,387
> zswap_reject_compress_fail 0 0
> zswap_reject_reclaim_fail 0 0
> IAA incompressible pages 188 349
> -------------------------------------------------------------------------------
>
>
> With the iaa_crypto driver changes for non-blocking descriptor allocations,
> no timeouts-with-mitigations were seen in compress/decompress jobs, for all
> of the above experiments.
>
>
> 64K folios: Kernel compilation/allmodconfig: zstd:
> ==================================================
>
> -------------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -------------------------------------------------------------------------------
> zswap compressor zstd zstd Improvement
> -------------------------------------------------------------------------------
> real_sec 880.62 850.41 -3.4%
> user_sec 15,717.23 15,683.17
> sys_sec 5,171.90 5,076.51 -1.8%
> -------------------------------------------------------------------------------
> Max_Res_Set_Size_KB 1,871,276 1,874,744
> -------------------------------------------------------------------------------
> memcg_high 0 0
> memcg_swap_fail 0 0
> 64kB_swpout_fallback 0 0
> zswpout 76,599,637 76,472,392
> zswpin 21,833,178 22,538,969
> pswpout 0 0
> pswpin 0 0
> ZSWPOUT-64kB 2,462,404 2,446,549
> SWPOUT-64kB 0 0
> pgmajfault 23,027,211 23,830,391
> zswap_reject_compress_fail 0 0
> zswap_reject_reclaim_fail 0 0
> -------------------------------------------------------------------------------
>
>
> 2M folios: Kernel compilation/allmodconfig: zstd:
> =================================================
>
> -------------------------------------------------------------------------------
> mm-unstable-10-24-2025 v13
> -------------------------------------------------------------------------------
> zswap compressor zstd zstd Improvement
> -------------------------------------------------------------------------------
> real_sec 888.45 849.54 -4.4%
> user_sec 15,841.87 15,828.10
> sys_sec 5,866.72 5,847.17 -0.3%
> -------------------------------------------------------------------------------
> Max_Res_Set_Size_KB 1,871,096 1,872,892
> -------------------------------------------------------------------------------
> memcg_high 0 0
> memcg_swap_fail 0 0
> thp_swpout_fallback 0 0
> zswpout 89,891,328 90,847,761
> zswpin 29,249,656 29,999,617
> pswpout 0 0
> pswpin 0 0
> ZSWPOUT-2048kB 12,198 12,481
> thp_swpout 0 0
> pgmajfault 30,077,425 30,915,945
> zswap_reject_compress_fail 0 0
> zswap_reject_reclaim_fail 0 0
> -------------------------------------------------------------------------------
>
>
>
> Changes since v12:
> ==================
> 1) Rebased to mm-unstable as of 10-24-2025, commit 813c0fa931ce.
> 2) Added "int nid" to zswap_entry to store the page's nid, to preserve zswap
> LRU list/shrinker behavior with bulk allocation, as suggested by Nhat and
> Yosry. No change in memory footprint of struct zswap_entry.
> 3) Added a WARN_ON() if kmem_cache_alloc_bulk() returns 0 or a number
> that's
> different than nr_entries, as suggested by Yosry.
> 4) Confirmed that kmem_cache_bulk_free() works for both bulk and non-bulk
> allocated entries, to follow-up on Yosry's comment.
> 5) Moved the call to cpuhp_state_remove_instance() to
> zswap_pool_destroy(), as
> suggested by Yosry.
> 6) Variable names changed to "nid" and "wb_enabled", per Yosry's
> suggestion.
> 7) Concise comments in zswap.c, and summarized commit logs, as suggested
> by
> Yosry.
> 8) Minimized branches in zswap_compress().
> 9) Deleted allocating extra memory in acomp_req->__ctx[] to statically store
> addresses to SG lists' lengths, as suggested by Herbert.
> 10) Deleted the iaa_comp API and export symbols, as suggested by Herbert.
> 11) Deleted @batch_size in struct crypto_acomp. Instead, the value is
> returned
> from struct acomp_alg directly, as suggested by Herbert.
> 12) Addressed checkpatch.pl warnings and coding style suggestions in the
> iaa_crypto patches, provided by Vinicius Gomes in internal code
> reviews. Thanks Vinicius!
>
>
> Changes since v11:
> ==================
> 1) Rebased to mm-unstable as of 9-18-2025, commit 1f98191f08b4.
> 2) Incorporated Herbert's suggestions on submitting the folio as the source
> and
> SG lists for the destination to create the compress batching interface from
> zswap to crypto.
> 3) As per Herbert's suggestion, added a new unit_size member to struct
> acomp_req, along with a acomp_request_set_unit_size() API for kernel
> modules
> to set the unit size to use while breaking down the request's src/dst
> scatterlists.
> 4) Implemented iaa_crypto batching using the new SG lists based architecture
> and
> crypto interfaces.
> 5) To make the SG lists based approach functional and performant for IAA, I
> have
> changed all the calls to dma_map_sg() to use nents of 1. This should not be
> a
> concern, since it eliminates redundant computes to scan an SG list with only
> one scatterlist for existing kernel users, i.e. zswap with the
> zswap_compress() modifications in this series. This will continue to hold
> true with the zram IAA batching support I am developing. There are no
> kernel
> use cases for the iaa_crypto driver that will break this assumption.
> 6) Addressed Herbert's comment about batch_size being a statically defined
> data
> member in struct acomp_alg and struct crypto_acomp.
> 7) Addressed Nhat's comment about VM_WARN_ON_ONCE(nr_pages >
> ZSWAP_MAX_BATCH_SIZE) in zswap_store_pages().
> 8) Nhat's comment about deleting struct swap_batch_decomp_data is
> automatically
> addressed by the SG lists based rewrite of the crypto batching interface.
> 9) Addressed Barry's comment about renaming pool->batch_size to
> pool->store_batch_size.
> 10) Incorporated Barry's suggestion to merge patches that introduce data
> members
> to structures and/or API and their usage.
> 11) Added performance data to patch 0023's commit log, as suggested by
> Barry.
>
> Changes since v10:
> ==================
> 1) Rebased to mm-unstable as of 7-30-2025, commit 01da54f10fdd.
> 2) Added change logging in patch 0024 on there being no Intel-specific
> dependencies in the batching framework, as suggested by
> Andrew Morton. Thanks Andrew!
> 3) Added change logging in patch 0024 on other ongoing work that can use
> batching, as per Andrew's suggestion. Thanks Andrew!
> 4) Added the IAA configuration script in the cover letter, as suggested
> by Nhat Pham. Thanks Nhat!
> 5) As suggested by Nhat, dropped patch 0020 from v10, that moves CPU
> hotplug procedures to pool functions.
> 6) Gathered kernel_compilation 'allmod' config performance data with
> writeback and zswap shrinker_enabled=Y.
> 7) Changed the pool->batch_size for software compressors to be
> ZSWAP_MAX_BATCH_SIZE since this gives better performance with the
> zswap
> shrinker enabled.
> 8) Was unable to replicate in v11 the issue seen in v10 with higher
> memcg_swap_fail than in the baseline, with usemem30/zstd.
>
> Changes since v9:
> =================
> 1) Rebased to mm-unstable as of 6-24-2025, commit 23b9c0472ea3.
> 2) iaa_crypto rearchitecting, mainline race condition fix, performance
> optimizations, code cleanup.
> 3) Addressed Herbert's comments in v9 patch 10, that an array based
> crypto_acomp interface is not acceptable.
> 4) Optimized the implementation of the batching zswap_compress() and
> zswap_store_pages() added in v9, to recover performance when
> integrated with the changes in commit 56e5a103a721 ("zsmalloc: prefer
> the the original page's node for compressed data").
>
> Changes since v8:
> =================
> 1) Rebased to mm-unstable as of 4-21-2025, commit 2c01d9f3c611.
> 2) Backported commits for reverting request chaining, since these are
> in cryptodev-2.6 but not yet in mm-unstable: without these backports,
> deflate-iaa is non-functional in mm-unstable:
> commit 64929fe8c0a4 ("crypto: acomp - Remove request chaining")
> commit 5976fe19e240 ("Revert "crypto: testmgr - Add multibuffer acomp
> testing"")
> Backported this hotfix as well:
> commit 002ba346e3d7 ("crypto: scomp - Fix off-by-one bug when
> calculating last page").
> 3) crypto_acomp_[de]compress() restored to non-request chained
> implementations since request chaining has been removed from acomp in
> commit 64929fe8c0a4 ("crypto: acomp - Remove request chaining").
> 4) New IAA WQ architecture to denote WQ type and whether or not a WQ
> should be shared among all package cores, or only to the "mapped"
> ones from an even cores-to-IAA distribution scheme.
> 5) Compress/decompress batching are implemented in iaa_crypto using new
> crypto_acomp_batch_compress()/crypto_acomp_batch_decompress() API.
> 6) Defines a "void *data" in struct acomp_req, based on Herbert advising
> against using req->base.data in the driver. This is needed for async
> submit-poll to work.
> 7) In zswap.c, moved the CPU hotplug callbacks to reside in "pool
> functions", per Yosry's suggestion to move procedures in a distinct
> patch before refactoring patches.
> 8) A new "u8 nr_reqs" member is added to "struct zswap_pool" to track
> the number of requests/buffers associated with the per-cpu acomp_ctx,
> as per Yosry's suggestion.
> 9) Simplifications to the acomp_ctx resources allocation, deletion,
> locking, and for these to exist from pool creation to pool deletion,
> based on v8 code review discussions with Yosry.
> 10) Use IS_ERR_OR_NULL() consistently in zswap_cpu_comp_prepare() and
> acomp_ctx_dealloc(), as per Yosry's v8 comment.
> 11) zswap_store_folio() is deleted, and instead, the loop over
> zswap_store_pages() is moved inline in zswap_store(), per Yosry's
> suggestion.
> 12) Better structure in zswap_compress(), unified procedure that
> compresses/stores a batch of pages for both, non-batching and
> batching compressors. Renamed from zswap_batch_compress() to
> zswap_compress(): Thanks Yosry for these suggestions.
>
>
> Changes since v7:
> =================
> 1) Rebased to mm-unstable as of 3-3-2025, commit 5f089a9aa987.
> 2) Changed the acomp_ctx->nr_reqs to be u8 since ZSWAP_MAX_BATCH_SIZE
> is
> defined as 8U, for saving memory in this per-cpu structure.
> 3) Fixed a typo in code comments in acomp_ctx_get_cpu_lock():
> acomp_ctx->initialized to acomp_ctx->__online.
> 4) Incorporated suggestions from Yosry, Chengming, Nhat and Johannes,
> thanks to all!
> a) zswap_batch_compress() replaces zswap_compress(). Thanks Yosry
> for this suggestion!
> b) Process the folio in sub-batches of ZSWAP_MAX_BATCH_SIZE, regardless
> of whether or not the compressor supports batching. This gets rid of
> the kmalloc(entries), and allows us to allocate an array of
> ZSWAP_MAX_BATCH_SIZE entries on the stack. This is implemented in
> zswap_store_pages().
> c) Use of a common structure and code paths for compressing a folio in
> batches, either as a request chain (in parallel in IAA hardware) or
> sequentially. No code duplication since zswap_compress() has been
> replaced with zswap_batch_compress(), simplifying maintainability.
> 5) A key difference between compressors that support batching and
> those that do not, is that for the latter, the acomp_ctx mutex is
> locked/unlocked per ZSWAP_MAX_BATCH_SIZE batch, so that
> decompressions
> to handle page-faults can make progress. This fixes the zstd kernel
> compilation regression seen in v7. For compressors that support
> batching, for e.g. IAA, the mutex is locked/released once for storing
> the folio.
> 6) Used likely/unlikely compiler directives and prefetchw to restore
> performance with the common code paths.
>
> Changes since v6:
> =================
> 1) Rebased to mm-unstable as of 2-27-2025, commit d58172d128ac.
>
> 2) Deleted crypto_acomp_batch_compress() and
> crypto_acomp_batch_decompress() interfaces, as per Herbert's
> suggestion. Batching is instead enabled by chaining the requests. For
> non-batching compressors, there is no request chaining involved. Both,
> batching and non-batching compressions are accomplished by zswap by
> calling:
>
> crypto_wait_req(crypto_acomp_compress(acomp_ctx->reqs[0]),
> &acomp_ctx->wait);
>
> 3) iaa_crypto implementation of batch compressions/decompressions using
> request chaining, as per Herbert's suggestions.
> 4) Simplification of the acomp_ctx resource allocation/deletion with
> respect to CPU hot[un]plug, to address Yosry's suggestions to explore the
> mutex options in zswap_cpu_comp_prepare(). Yosry, please let me know if
> the per-cpu memory cost of this proposed change is acceptable (IAA:
> 64.8KB, Software compressors: 8.2KB). On the positive side, I believe
> restarting reclaim on a CPU after it has been through an offline-online
> transition, will be much faster by not deleting the acomp_ctx resources
> when the CPU gets offlined.
> 5) Use of lockdep assertions rather than comments for internal locking
> rules, as per Yosry's suggestion.
> 6) No specific references to IAA in zswap.c, as suggested by Yosry.
> 7) Explored various solutions other than the v6 zswap_store_folio()
> implementation, to fix the zstd regression seen in v5, to attempt to
> unify common code paths, and to allocate smaller arrays for the zswap
> entries on the stack. All these options were found to cause usemem30
> latency regression with zstd. The v6 version of zswap_store_folio() is
> the only implementation that does not cause zstd regression, confirmed
> by 10 consecutive runs, each giving quite consistent latency
> numbers. Hence, the v6 implementation is carried forward to v7, with
> changes for branching for batching vs. sequential compression API
> calls.
>
>
> Changes since v5:
> =================
> 1) Rebased to mm-unstable as of 2-1-2025, commit 7de6fd8ab650.
>
> Several improvements, regression fixes and bug fixes, based on Yosry's
> v5 comments (Thanks Yosry!):
>
> 2) Fix for zstd performance regression in v5.
> 3) Performance debug and fix for marginal improvements with IAA batching
> vs. sequential.
> 4) Performance testing data compares IAA with and without batching, instead
> of IAA batching against zstd.
> 5) Commit logs/zswap comments not mentioning crypto_acomp
> implementation
> details.
> 6) Delete the pr_info_once() when batching resources are allocated in
> zswap_cpu_comp_prepare().
> 7) Use kcalloc_node() for the multiple acomp_ctx buffers/reqs in
> zswap_cpu_comp_prepare().
> 8) Simplify and consolidate error handling cleanup code in
> zswap_cpu_comp_prepare().
> 9) Introduce zswap_compress_folio() in a separate patch.
> 10) Bug fix in zswap_store_folio() when xa_store() failure can cause all
> compressed objects and entries to be freed, and UAF when zswap_store()
> tries to free the entries that were already added to the xarray prior
> to the failure.
> 11) Deleting compressed_bytes/bytes. zswap_store_folio() also comprehends
> the recent fixes in commit bf5eaaaf7941 ("mm/zswap: fix inconsistency
> when zswap_store_page() fails") by Hyeonggon Yoo.
>
> iaa_crypto improvements/fixes/changes:
>
> 12) Enables asynchronous mode and makes it the default. With commit
> 4ebd9a5ca478 ("crypto: iaa - Fix IAA disabling that occurs when
> sync_mode is set to 'async'"), async mode was previously just sync. We
> now have true async support.
> 13) Change idxd descriptor allocations from blocking to non-blocking with
> timeouts, and mitigations for compress/decompress ops that fail to
> obtain a descriptor. This is a fix for tasks blocked errors seen in
> configurations where 30+ cores are running workloads under high memory
> pressure, and sending comps/decomps to 1 IAA device.
> 14) Fixes a bug with unprotected access of "deflate_generic_tfm" in
> deflate_generic_decompress(), which can cause data corruption and
> zswap_decompress() kernel crash.
> 15) zswap uses crypto_acomp_batch_compress() with async polling instead of
> request chaining for slightly better latency. However, the request
> chaining framework itself is unchanged, preserved from v5.
>
>
> Changes since v4:
> =================
> 1) Rebased to mm-unstable as of 12-20-2024, commit 5555a83c82d6.
> 2) Added acomp request chaining, as suggested by Herbert. Thanks Herbert!
> 3) Implemented IAA compress batching using request chaining.
> 4) zswap_store() batching simplifications suggested by Chengming, Yosry and
> Nhat, thanks to all!
> - New zswap_compress_folio() that is called by zswap_store().
> - Move the loop over folio's pages out of zswap_store() and into a
> zswap_store_folio() that stores all pages.
> - Allocate all zswap entries for the folio upfront.
> - Added zswap_batch_compress().
> - Branch to call zswap_compress() or zswap_batch_compress() inside
> zswap_compress_folio().
> - All iterations over pages kept in same function level.
> - No helpers other than the newly added zswap_store_folio() and
> zswap_compress_folio().
>
>
> Changes since v3:
> =================
> 1) Rebased to mm-unstable as of 11-18-2024, commit 5a7056135bb6.
> 2) Major re-write of iaa_crypto driver's mapping of IAA devices to cores,
> based on packages instead of NUMA nodes.
> 3) Added acomp_has_async_batching() API to crypto acomp, that allows
> zswap/zram to query if a crypto_acomp has registered batch_compress and
> batch_decompress interfaces.
> 4) Clear the poll bits on the acomp_reqs passed to
> iaa_comp_a[de]compress_batch() so that a module like zswap can be
> confident about the acomp_reqs[0] not having the poll bit set before
> calling the fully synchronous API crypto_acomp_[de]compress().
> Herbert, I would appreciate it if you can review changes 2-4; in patches
> 1-8 in v4. I did not want to introduce too many iaa_crypto changes in
> v4, given that patch 7 is already making a major change. I plan to work
> on incorporating the request chaining using the ahash interface in v5
> (I need to understand the basic crypto ahash better). Thanks Herbert!
> 5) Incorporated Johannes' suggestion to not have a sysctl to enable
> compress batching.
> 6) Incorporated Yosry's suggestion to allocate batching resources in the
> cpu hotplug onlining code, since there is no longer a sysctl to control
> batching. Thanks Yosry!
> 7) Incorporated Johannes' suggestions related to making the overall
> sequence of events between zswap_store() and zswap_batch_store()
> similar
> as much as possible for readability and control flow, better naming of
> procedures, avoiding forward declarations, not inlining error path
> procedures, deleting zswap internal details from zswap.h, etc. Thanks
> Johannes, really appreciate the direction!
> I have tried to explain the minimal future-proofing in terms of the
> zswap_batch_store() signature and the definition of "struct
> zswap_batch_store_sub_batch" in the comments for this struct. I hope the
> new code explains the control flow a bit better.
>
>
> Changes since v2:
> =================
> 1) Rebased to mm-unstable as of 11-5-2024, commit 7994b7ea6ac8.
> 2) Fixed an issue in zswap_create_acomp_ctx() with checking for NULL
> returned by kmalloc_node() for acomp_ctx->buffers and for
> acomp_ctx->reqs.
> 3) Fixed a bug in zswap_pool_can_batch() for returning true if
> pool->can_batch_comp is found to be equal to BATCH_COMP_ENABLED,
> and if
> the per-cpu acomp_batch_ctx tests true for batching resources having
> been allocated on this cpu. Also, changed from per_cpu_ptr() to
> raw_cpu_ptr().
> 4) Incorporated the zswap_store_propagate_errors() compilation warning fix
> suggested by Dan Carpenter. Thanks Dan!
> 5) Replaced the references to SWAP_CRYPTO_SUB_BATCH_SIZE in comments
> in
> zswap.h, with SWAP_CRYPTO_BATCH_SIZE.
>
> Changes since v1:
> =================
> 1) Rebased to mm-unstable as of 11-1-2024, commit 5c4cf96cd702.
> 2) Incorporated Herbert's suggestions to use an acomp_req flag to indicate
> async/poll mode, and to encapsulate the polling functionality in the
> iaa_crypto driver. Thanks Herbert!
> 3) Incorporated Herbert's and Yosry's suggestions to implement the batching
> API in iaa_crypto and to make its use seamless from zswap's
> perspective. Thanks Herbert and Yosry!
> 4) Incorporated Yosry's suggestion to make it more convenient for the user
> to enable compress batching, while minimizing the memory footprint
> cost. Thanks Yosry!
> 5) Incorporated Yosry's suggestion to de-couple the shrink_folio_list()
> reclaim batching patch from this series, since it requires a broader
> discussion.
>
>
> IAA configuration script "enable_iaa.sh":
> =========================================
>
> Acknowledgements: Binuraj Ravindran and Rakib Al-Fahad.
>
> Usage:
> ------
>
> ./enable_iaa.sh -d <num_IAAs> -q <num_WQs_per_IAA>
>
>
> #---------------------------------<cut here>----------------------------------
> #!/usr/bin/env bash
> #SPDX-License-Identifier: BSD-3-Clause
> #Copyright (c) 2025, Intel Corporation
> #Description: Configure IAA devices
>
> VERIFY_COMPRESS_PATH="/sys/bus/dsa/drivers/crypto/verify_compress"
>
> iax_dev_id="0cfe"
> num_iaa=$(lspci -d:${iax_dev_id} | wc -l)
> sockets=$(lscpu | grep Socket | awk '{print $2}')
> echo "Found ${num_iaa} instances in ${sockets} sockets(s)"
>
> # The same number of devices will be configured in each socket, if there
> # are more than one socket.
> # Normalize with respect to the number of sockets.
> device_num_per_socket=$(( num_iaa/sockets ))
> num_iaa_per_socket=$(( num_iaa / sockets ))
>
> iaa_wqs=2
> verbose=0
> iaa_engines=8
> mode="dedicated"
> wq_type="kernel"
> iaa_crypto_mode="async"
> verify_compress=0
>
>
> # Function to handle errors
> handle_error() {
> echo "Error: $1"
> exit 1
> }
>
> # Process arguments
>
> while getopts "d:hm:q:vD" opt; do
> case $opt in
> d)
> device_num_per_socket=$OPTARG
> ;;
> m)
> iaa_crypto_mode=$OPTARG
> ;;
> q)
> iaa_wqs=$OPTARG
> ;;
> D)
> verbose=1
> ;;
> v)
> verify_compress=1
> ;;
> h)
> echo "Usage: $0 [-d <device_count>][-q <wq_per_device>][-v]"
> echo " -d - number of devices"
> echo " -q - number of WQs per device"
> echo " -v - verbose mode"
> echo " -h - help"
> exit
> ;;
> \?)
> echo "Invalid option: -$OPTARG" >&2
> exit
> ;;
> esac
> done
>
> LOG="configure_iaa.log"
>
> # Update wq_size based on number of wqs
> wq_size=$(( 128 / iaa_wqs ))
>
> # Take care of the enumeration, if DSA is enabled.
> dsa=`lspci | grep -c 0b25`
> # set first,step counters to correctly enumerate iax devices based on
> # whether running on guest or host with or without dsa
> first=0
> step=1
> [[ $dsa -gt 0 && -d /sys/bus/dsa/devices/dsa0 ]] && first=1 && step=2
> echo "first index: ${first}, step: ${step}"
>
>
> #
> # Switch to software compressors and disable IAAs to have a clean start
> #
> COMPRESSOR=/sys/module/zswap/parameters/compressor
> last_comp=`cat ${COMPRESSOR}`
> echo lzo > ${COMPRESSOR}
>
> echo "Disable IAA devices before configuring"
>
> for ((i = ${first}; i < ${step} * ${num_iaa}; i += ${step})); do
> for ((j = 0; j < ${iaa_wqs}; j += 1)); do
> cmd="accel-config disable-wq iax${i}/wq${i}.${j} >& /dev/null"
> [[ $verbose == 1 ]] && echo $cmd; eval $cmd
> done
> cmd="accel-config disable-device iax${i} >& /dev/null"
> [[ $verbose == 1 ]] && echo $cmd; eval $cmd
> done
>
> rmmod iaa_crypto
> modprobe iaa_crypto
>
> # apply crypto parameters
> echo $verify_compress > ${VERIFY_COMPRESS_PATH} || handle_error "did
> not change verify_compress"
> # Note: This is a temporary solution for during the kernel transition.
> if [ -f /sys/bus/dsa/drivers/crypto/g_comp_wqs_per_iaa ];then
> echo 1 > /sys/bus/dsa/drivers/crypto/g_comp_wqs_per_iaa ||
> handle_error "did not set g_comp_wqs_per_iaa"
> elif [ -f /sys/bus/dsa/drivers/crypto/g_wqs_per_iaa ];then
> echo 1 > /sys/bus/dsa/drivers/crypto/g_wqs_per_iaa || handle_error "did
> not set g_wqs_per_iaa"
> fi
> if [ -f /sys/bus/dsa/drivers/crypto/g_consec_descs_per_gwq ];then
> echo 1 > /sys/bus/dsa/drivers/crypto/g_consec_descs_per_gwq ||
> handle_error "did not set g_consec_descs_per_gwq"
> fi
> echo ${iaa_crypto_mode} > /sys/bus/dsa/drivers/crypto/sync_mode ||
> handle_error "could not set sync_mode"
>
>
>
> echo "Configuring ${device_num_per_socket} device(s) out of
> $num_iaa_per_socket per socket"
> if [ "${device_num_per_socket}" -le "${num_iaa_per_socket}" ]; then
> echo "Configuring all devices"
> start=${first}
> end=$(( ${step} * ${device_num_per_socket} ))
> else
> echo "ERROR: Not enough devices"
> exit
> fi
>
>
> #
> # enable all iax devices and wqs
> #
> for (( socket = 0; socket < ${sockets}; socket += 1 )); do
> for ((i = ${start}; i < ${end}; i += ${step})); do
>
> echo "Configuring iaa$i on socket ${socket}"
>
> for ((j = 0; j < ${iaa_engines}; j += 1)); do
> cmd="accel-config config-engine iax${i}/engine${i}.${j} --group-id=0"
> [[ $verbose == 1 ]] && echo $cmd; eval $cmd
> done
>
> # Config WQs
> for ((j = 0; j < ${iaa_wqs}; j += 1)); do
> # Config WQ: group 0, priority=10, mode=shared, type = kernel
> name=kernel, driver_name=crypto
> cmd="accel-config config-wq iax${i}/wq${i}.${j} -g 0 -s ${wq_size} -p 10 -
> m ${mode} -y ${wq_type} -n iaa_crypto${i}${j} -d crypto"
> [[ $verbose == 1 ]] && echo $cmd; eval $cmd
> done
>
> # Enable Device and WQs
> cmd="accel-config enable-device iax${i}"
> [[ $verbose == 1 ]] && echo $cmd; eval $cmd
>
> for ((j = 0; j < ${iaa_wqs}; j += 1)); do
> cmd="accel-config enable-wq iax${i}/wq${i}.${j}"
> [[ $verbose == 1 ]] && echo $cmd; eval $cmd
> done
>
> done
> start=$(( start + ${step} * ${num_iaa_per_socket} ))
> end=$(( start + (${step} * ${device_num_per_socket}) ))
> done
>
> # Restore the last compressor
> echo "$last_comp" > ${COMPRESSOR}
>
> # Check if the configuration is correct
> echo "Configured IAA devices:"
> accel-config list | grep iax
>
> #---------------------------------<cut here>----------------------------------
>
>
> I would greatly appreciate code review comments for the iaa_crypto driver
> and mm patches included in this series!
>
> Thanks,
> Kanchana
>
>
>
> Kanchana P Sridhar (22):
> crypto: iaa - Reorganize the iaa_crypto driver code.
> crypto: iaa - New architecture for IAA device WQ comp/decomp usage &
> core mapping.
> crypto: iaa - Simplify, consistency of function parameters, minor
> stats bug fix.
> crypto: iaa - Descriptor allocation timeouts with mitigations.
> crypto: iaa - iaa_wq uses percpu_refs for get/put reference counting.
> crypto: iaa - Simplify the code flow in iaa_compress() and
> iaa_decompress().
> crypto: iaa - Refactor hardware descriptor setup into separate
> procedures.
> crypto: iaa - Simplified, efficient job submissions for non-irq mode.
> crypto: iaa - Deprecate exporting add/remove IAA compression modes.
> crypto: iaa - Expect a single scatterlist for a [de]compress request's
> src/dst.
> crypto: iaa - Rearchitect iaa_crypto to have clean interfaces with
> crypto_acomp
> crypto: acomp - Define a unit_size in struct acomp_req to enable
> batching.
> crypto: iaa - IAA Batching for parallel compressions/decompressions.
> crypto: iaa - Enable async mode and make it the default.
> crypto: iaa - Disable iaa_verify_compress by default.
> crypto: iaa - Submit the two largest source buffers first in
> decompress batching.
> crypto: iaa - Add deflate-iaa-dynamic compression mode.
> crypto: acomp - Add crypto_acomp_batch_size() to get an algorithm's
> batch-size.
> mm: zswap: Per-CPU acomp_ctx resources exist from pool creation to
> deletion.
> mm: zswap: Consistently use IS_ERR_OR_NULL() to check acomp_ctx
> resources.
> mm: zswap: zswap_store() will process a large folio in batches.
> mm: zswap: Batched zswap_compress() with compress batching of large
> folios.
>
> .../driver-api/crypto/iaa/iaa-crypto.rst | 168 +-
> crypto/acompress.c | 14 +
> crypto/testmgr.c | 10 +
> crypto/testmgr.h | 74 +
> drivers/crypto/intel/iaa/Makefile | 4 +-
> drivers/crypto/intel/iaa/iaa_crypto.h | 87 +-
> .../intel/iaa/iaa_crypto_comp_dynamic.c | 22 +
> drivers/crypto/intel/iaa/iaa_crypto_main.c | 2836 ++++++++++++-----
> drivers/crypto/intel/iaa/iaa_crypto_stats.c | 8 +
> drivers/crypto/intel/iaa/iaa_crypto_stats.h | 2 +
> include/crypto/acompress.h | 48 +
> include/crypto/internal/acompress.h | 3 +
> mm/zswap.c | 700 ++--
> 13 files changed, 2905 insertions(+), 1071 deletions(-)
> create mode 100644 drivers/crypto/intel/iaa/iaa_crypto_comp_dynamic.c
>
> --
> 2.27.0
Powered by blists - more mailing lists