RE: [PATCH v7 00/15] zswap IAA compress batching

["Sridhar, Kanchana P" <kanchana.p.sridhar@intel.com>]

> -----Original Message-----
> From: Sridhar, Kanchana P <kanchana.p.sridhar@intel.com>
> Sent: Friday, February 28, 2025 5:18 PM
> To: Yosry Ahmed <yosry.ahmed@linux.dev>
> Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> hannes@cmpxchg.org; nphamcs@gmail.com; chengming.zhou@linux.dev;
> usamaarif642@gmail.com; ryan.roberts@arm.com; 21cnbao@gmail.com;
> ying.huang@linux.alibaba.com; akpm@linux-foundation.org; linux-
> crypto@vger.kernel.org; herbert@gondor.apana.org.au;
> davem@davemloft.net; clabbe@baylibre.com; ardb@kernel.org;
> ebiggers@google.com; surenb@google.com; Accardi, Kristen C
> <kristen.c.accardi@intel.com>; Feghali, Wajdi K <wajdi.k.feghali@intel.com>;
> Gopal, Vinodh <vinodh.gopal@intel.com>; Sridhar, Kanchana P
> <kanchana.p.sridhar@intel.com>
> Subject: RE: [PATCH v7 00/15] zswap IAA compress batching
> 
> 
> > -----Original Message-----
> > From: Yosry Ahmed <yosry.ahmed@linux.dev>
> > Sent: Friday, February 28, 2025 5:13 PM
> > To: Sridhar, Kanchana P <kanchana.p.sridhar@intel.com>
> > Cc: linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> > hannes@cmpxchg.org; nphamcs@gmail.com; chengming.zhou@linux.dev;
> > usamaarif642@gmail.com; ryan.roberts@arm.com; 21cnbao@gmail.com;
> > ying.huang@linux.alibaba.com; akpm@linux-foundation.org; linux-
> > crypto@vger.kernel.org; herbert@gondor.apana.org.au;
> > davem@davemloft.net; clabbe@baylibre.com; ardb@kernel.org;
> > ebiggers@google.com; surenb@google.com; Accardi, Kristen C
> > <kristen.c.accardi@intel.com>; Feghali, Wajdi K
> <wajdi.k.feghali@intel.com>;
> > Gopal, Vinodh <vinodh.gopal@intel.com>
> > Subject: Re: [PATCH v7 00/15] zswap IAA compress batching
> >
> > On Sat, Mar 01, 2025 at 01:09:22AM +0000, Sridhar, Kanchana P wrote:
> > > Hi All,
> > >
> > > > Performance testing (Kernel compilation, allmodconfig):
> > > > =======================================================
> > > >
> > > > The experiments with kernel compilation test, 32 threads, in tmpfs use
> the
> > > > "allmodconfig" that takes ~12 minutes, and has considerable
> > swapout/swapin
> > > > activity. The cgroup's memory.max is set to 2G.
> > > >
> > > >
> > > >  64K folios: Kernel compilation/allmodconfig:
> > > >  ============================================
> > > >
> > > >  -------------------------------------------------------------------------------
> > > >                      mm-unstable               v7   mm-unstable            v7
> > > >  -------------------------------------------------------------------------------
> > > >  zswap compressor    deflate-iaa      deflate-iaa          zstd          zstd
> > > >  -------------------------------------------------------------------------------
> > > >  real_sec                 775.83           765.90        769.39        772.63
> > > >  user_sec              15,659.10        15,659.14     15,666.28     15,665.98
> > > >  sys_sec                4,209.69         4,040.44      5,277.86      5,358.61
> > > >  -------------------------------------------------------------------------------
> > > >  Max_Res_Set_Size_KB   1,871,116        1,874,128     1,873,200
> 1,873,488
> > > >  -------------------------------------------------------------------------------
> > > >  memcg_high                    0                0             0             0
> > > >  memcg_swap_fail               0                0             0             0
> > > >  zswpout             107,305,181      106,985,511    86,621,912    89,355,274
> > > >  zswpin               32,418,991       32,184,517    25,337,514    26,522,042
> > > >  pswpout                     272               80            94            16
> > > >  pswpin                      274               69            54            16
> > > >  thp_swpout                    0                0             0             0
> > > >  thp_swpout_fallback           0                0             0             0
> > > >  64kB_swpout_fallback        494                0             0             0
> > > >  pgmajfault           34,577,545       34,333,290    26,892,991    28,132,682
> > > >  ZSWPOUT-64kB          3,498,796        3,460,751     2,737,544     2,823,211
> > > >  SWPOUT-64kB                  17                4             4             1
> > > >  -------------------------------------------------------------------------------
> > > >
> > > > [...]
> > > >
> > > > Summary:
> > > > ========
> > > > The performance testing data with usemem 30 processes and kernel
> > > > compilation test show 61%-73% throughput gains and 27%-37% sys time
> > > > reduction (usemem30) and 4% sys time reduction (kernel compilation)
> > with
> > > > zswap_store() large folios using IAA compress batching as compared to
> > > > IAA sequential. There is no performance regression for zstd/usemem30
> > and a
> > > > slight 1.5% sys time zstd regression with kernel compilation allmod
> > > > config.
> > >
> > > I think I know why kernel_compilation with zstd shows a regression
> whereas
> > > usemem30 does not. It is because I lock/unlock the acomp_ctx mutex
> once
> > > per folio. This can cause decomp jobs to wait for the mutex, which can
> cause
> > > more compressions, and this repeats. kernel_compilation has 25M+
> > decomps
> > > with zstd, whereas usemem30 has practically no decomps, but is
> > > compression-intensive, because of which it benefits the once-per-folio
> lock
> > > acquire/release.
> > >
> > > I am testing a fix where I return zswap_compress() to do the mutex
> > lock/unlock,
> > > and expect to post v8 by end of the day. I would appreciate it if you can
> hold
> > off
> > > on reviewing only the zswap patches [14, 15] in my v7 and instead review
> > the v8
> > > versions of these two patches.
> >
> > I was planning to take a look at v7 next week, so take your time, no
> > rush to post it on a Friday afternoon.
> >
> > Anyway, thanks for the heads up, I appreciate you trying to save
> > everyone's time.
> 
> Thanks Yosry!

Hi Yosry, All,

I posted a v8 of this patch-series with a fix for the zstd kernel compilation regression,
and consolidation of common code between non-batching and batching
compressors, to follow up on suggestions from Yosry, Chengming, Nhat and Johannes.

You can disregard v7 and review v8 instead.

Thanks,
Kanchana