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Message-ID: <CAKEwX=PS7mjuhaazydkE2TOVa5DWQu9521FqH4aXi0yptZQaeA@mail.gmail.com> Date: Fri, 30 Jan 2026 17:12:35 -0800 From: Nhat Pham <nphamcs@...il.com> To: Kanchana P Sridhar <kanchana.p.sridhar@...el.com> Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, hannes@...xchg.org, yosry.ahmed@...ux.dev, 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, kristen.c.accardi@...el.com, vinicius.gomes@...el.com, giovanni.cabiddu@...el.com, wajdi.k.feghali@...el.com Subject: Re: [PATCH v14 26/26] mm: zswap: Batched zswap_compress() for compress batching of large folios. On Sat, Jan 24, 2026 at 7:36 PM Kanchana P Sridhar <kanchana.p.sridhar@...el.com> wrote: > > We introduce a new 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. > > The vectorized implementation of calling the earlier zswap_compress() > sequentially, one page at a time in zswap_store_pages(), is replaced > with this new version of zswap_compress() that accepts multiple pages to > compress as a batch. > > If the compressor does not support batching, each page in the batch is > compressed and stored sequentially. If the compressor supports batching, > for e.g., 'deflate-iaa', the Intel IAA hardware accelerator, the batch > is compressed in parallel in hardware. > > If the batch is compressed without errors, the compressed buffers for > the batch are stored in zsmalloc. In case of compression errors, the > current behavior based on whether the folio is enabled for zswap > writeback, is preserved. > > The batched zswap_compress() incorporates Herbert's suggestion for > SG lists to represent the batch's inputs/outputs to interface with the > crypto API [1]. > > Performance data: > ================= > As suggested by Barry, this is the performance data gathered on Intel > Sapphire Rapids with two workloads: > > 1) 30 usemem processes in a 150 GB memory limited cgroup, each > allocates 10G, i.e, effectively running at 50% memory pressure. > 2) kernel_compilation "defconfig", 32 threads, cgroup memory limit set > to 1.7 GiB (50% memory pressure, since baseline memory usage is 3.4 > GiB): data averaged across 10 runs. > > To keep comparisons simple, all testing was done without the > zswap shrinker. > > ========================================================================= > IAA mm-unstable-1-23-2026 v14 > ========================================================================= > zswap compressor deflate-iaa deflate-iaa IAA Batching > vs. > IAA Sequential > ========================================================================= > usemem30, 64K folios: > > Total throughput (KB/s) 6,226,967 10,551,714 69% > Average throughput (KB/s) 207,565 351,723 69% > elapsed time (sec) 99.19 67.45 -32% > sys time (sec) 2,356.19 1,580.47 -33% > > usemem30, PMD folios: > > Total throughput (KB/s) 6,347,201 11,315,500 78% > Average throughput (KB/s) 211,573 377,183 78% > elapsed time (sec) 88.14 63.37 -28% > sys time (sec) 2,025.53 1,455.23 -28% > > kernel_compilation, 64K folios: > > elapsed time (sec) 100.10 98.74 -1.4% > sys time (sec) 308.72 301.23 -2% > > kernel_compilation, PMD folios: > > elapsed time (sec) 95.29 93.44 -1.9% > sys time (sec) 346.21 344.48 -0.5% > ========================================================================= > > ========================================================================= > ZSTD mm-unstable-1-23-2026 v14 > ========================================================================= > zswap compressor zstd zstd v14 ZSTD > Improvement > ========================================================================= > usemem30, 64K folios: > > Total throughput (KB/s) 6,032,326 6,047,448 0.3% > Average throughput (KB/s) 201,077 201,581 0.3% > elapsed time (sec) 97.52 95.33 -2.2% > sys time (sec) 2,415.40 2,328.38 -4% > > usemem30, PMD folios: > > Total throughput (KB/s) 6,570,404 6,623,962 0.8% > Average throughput (KB/s) 219,013 220,798 0.8% > elapsed time (sec) 89.17 88.25 -1% > sys time (sec) 2,126.69 2,043.08 -4% > > kernel_compilation, 64K folios: > > elapsed time (sec) 100.89 99.98 -0.9% > sys time (sec) 417.49 414.62 -0.7% > > kernel_compilation, PMD folios: > > elapsed time (sec) 98.26 97.38 -0.9% > sys time (sec) 487.14 473.16 -2.9% > ========================================================================= The rest of the patch changelog (architectural and future considerations) can stay in the cover letter. Let's not duplicate information :) Keep the patch changelog limited to only the changes in the patch itself (unless we need some clarifications imminently relevant). I'll review the remainder of the patch later :)
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