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Message-ID: <SJ2PR11MB847268ABD6F084E87CC5F5A4C99DA@SJ2PR11MB8472.namprd11.prod.outlook.com> Date: Sun, 1 Feb 2026 02:53:18 +0000 From: "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com> To: Nhat Pham <nphamcs@...il.com> CC: "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>, "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>, "Cabiddu, Giovanni" <giovanni.cabiddu@...el.com>, "Feghali, Wajdi K" <wajdi.k.feghali@...el.com>, "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com> Subject: RE: [PATCH v14 26/26] mm: zswap: Batched zswap_compress() for compress batching of large folios. > -----Original Message----- > From: Nhat Pham <nphamcs@...il.com> > Sent: Saturday, January 31, 2026 4:49 PM > To: Sridhar, Kanchana P <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; Accardi, Kristen C > <kristen.c.accardi@...el.com>; Gomes, Vinicius <vinicius.gomes@...el.com>; > Cabiddu, Giovanni <giovanni.cabiddu@...el.com>; Feghali, Wajdi K > <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 31, 2026 at 12:32 PM Sridhar, Kanchana P > <kanchana.p.sridhar@...el.com> wrote: > > > > > > > -----Original Message----- > > > From: Nhat Pham <nphamcs@...il.com> > > > Sent: Friday, January 30, 2026 5:13 PM > > > To: Sridhar, Kanchana P <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; Accardi, Kristen C > > > <kristen.c.accardi@...el.com>; Gomes, Vinicius > <vinicius.gomes@...el.com>; > > > Cabiddu, Giovanni <giovanni.cabiddu@...el.com>; Feghali, Wajdi K > > > <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). > > > > Hi Nhat, > > > > Thanks for this comment. Yosry had also pointed this out in [1]. I have > > been including the architectural and future considerations in this change log > > since Andrew had asked me to do so. I hope this is Ok? > > Ah hmmmmm. For some reasons I was under the assumption that usually > Andrew would concatenate the patch cover letter and the patch > changelog before merging. Oh well. > > If Andrew prefers including that here then I'm fine with it. Ok, thank you Nhat! Best regards, Kanchana > > > > > [1]: https://patchwork.kernel.org/comment/26706240/ > > > > > > > > I'll review the remainder of the patch later :) > > > > Sure. > > > > Thanks, > > Kanchana
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