RE: [RFC PATCH v1 00/13] zswap IAA compress batching

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Hi Yosry,

> -----Original Message-----
> From: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> Sent: Tuesday, October 22, 2024 5:57 PM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx>
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> Subject: Re: [RFC PATCH v1 00/13] zswap IAA compress batching
> 
> On Thu, Oct 17, 2024 at 11:41 PM Kanchana P Sridhar
> <kanchana.p.sridhar@xxxxxxxxx> wrote:
> >
> >
> > IAA Compression Batching:
> > =========================
> >
> > This RFC patch-series introduces the use of the Intel Analytics Accelerator
> > (IAA) for parallel compression of pages in a folio, and for batched reclaim
> > of hybrid any-order batches of folios in shrink_folio_list().
> >
> > The patch-series is organized as follows:
> >
> >  1) iaa_crypto driver enablers for batching: Relevant patches are tagged
> >     with "crypto:" in the subject:
> >
> >     a) async poll crypto_acomp interface without interrupts.
> >     b) crypto testmgr acomp poll support.
> >     c) Modifying the default sync_mode to "async" and disabling
> >        verify_compress by default, to facilitate users to run IAA easily for
> >        comparison with software compressors.
> >     d) Changing the cpu-to-iaa mappings to more evenly balance cores to IAA
> >        devices.
> >     e) Addition of a "global_wq" per IAA, which can be used as a global
> >        resource for the socket. If the user configures 2WQs per IAA device,
> >        the driver will distribute compress jobs from all cores on the
> >        socket to the "global_wqs" of all the IAA devices on that socket, in
> >        a round-robin manner. This can be used to improve compression
> >        throughput for workloads that see a lot of swapout activity.
> >
> >  2) Migrating zswap to use async poll in zswap_compress()/decompress().
> >  3) A centralized batch compression API that can be used by swap modules.
> >  4) IAA compress batching within large folio zswap stores.
> >  5) IAA compress batching of any-order hybrid folios in
> >     shrink_folio_list(). The newly added "sysctl vm.compress-batchsize"
> >     parameter can be used to configure the number of folios in [1, 32] to
> >     be reclaimed using compress batching.
> 
> I am still digesting this series but I have some high level questions
> that I left on some patches. My intuition though is that we should
> drop (5) from the initial proposal as it's most controversial.
> Batching reclaim of unrelated folios through zswap *might* make sense,
> but it needs a broader conversation and it needs justification on its
> own merit, without the rest of the series.

Thanks for these suggestions!  Sure, I can drop (5) from the initial patch-set.
Agree also, this needs a broader discussion.

I believe the 4K folios usemem30 data in this patchset does bring across
the batching reclaim benefits to provide justification on its own merit. I added
the data on batching reclaim with kernel compilation as part of the 4K folios
experiments in the IAA decompression batching patch-series [1].
Listing it here as well. I will make sure to add this data in subsequent revs.

--------------------------------------------------------------------------
 Kernel compilation in tmpfs/allmodconfig, 2G max memory:
 
 No large folios          mm-unstable-10-16-2024       shrink_folio_list()        
                                                       batching of folios     
 --------------------------------------------------------------------------
 zswap compressor         zstd       deflate-iaa       deflate-iaa   
 vm.compress-batchsize     n/a               n/a                32   
 vm.page-cluster             3                 3                 3   
 --------------------------------------------------------------------------
 real_sec               783.87            761.69            747.32   
 user_sec            15,750.07         15,716.69         15,728.39   
 sys_sec              6,522.32          5,725.28          5,399.44   
 Max_RSS_KB          1,872,640         1,870,848         1,874,432   
                                                                            
 zswpout            82,364,991        97,739,600       102,780,612   
 zswpin             21,303,393        27,684,166        29,016,252   
 pswpout                    13               222               213   
 pswpin                     12               209               202   
 pgmajfault         17,114,339        22,421,211        23,378,161   
 swap_ra             4,596,035         5,840,082         6,231,646   
 swap_ra_hit         2,903,249         3,682,444         3,940,420   
 --------------------------------------------------------------------------

The performance improvements seen does depend on compression batching in
the swap modules (zswap). The implementation in patch 12 in the compress
batching series sets up this zswap compression pipeline, that takes an array of
folios and processes them in batches of 8 pages compressed in parallel in hardware.
That being said, we do see latency improvements even with reclaim batching
combined with zswap compress batching with zstd/lzo-rle/etc. I haven't done a
lot of analysis of this, but I am guessing fewer calls from the swap layer
(swap_writepage()) into zswap could have something to do with this. If we believe
that batching can be the right thing to do even for the software compressors,
I can gather batching data with zstd for v2.


[1] https://patchwork.kernel.org/project/linux-mm/cover/20241018064805.336490-1-kanchana.p.sridhar@xxxxxxxxx/

Thanks,
Kanchana

> 
> >
> > IAA compress batching can be enabled only on platforms that have IAA, by
> > setting this config variable:
> >
> >  CONFIG_ZSWAP_STORE_BATCHING_ENABLED="y"
> >
> > The performance testing data with usemem 30 instances shows throughput
> > gains of up to 40%, elapsed time reduction of up to 22% and sys time
> > reduction of up to 30% with IAA compression batching.
> >
> > Our internal validation of IAA compress/decompress batching in highly
> > contended Sapphire Rapids server setups with workloads running on 72
> cores
> > for ~25 minutes under stringent memory limit constraints have shown up to
> > 50% reduction in sys time and 3.5% reduction in workload run time as
> > compared to software compressors.
> >
> >
> > System setup for testing:
> > =========================
> > Testing of this patch-series was done with mm-unstable as of 10-16-2024,
> > commit 817952b8be34, without and with this patch-series.
> > Data was gathered on an Intel Sapphire Rapids server, dual-socket 56 cores
> > per socket, 4 IAA devices per socket, 503 GiB RAM and 525G SSD disk
> > partition swap. Core frequency was fixed at 2500MHz.
> >
> > The vm-scalability "usemem" test was run in a cgroup whose memory.high
> > was fixed at 150G. The 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 -s 10 -n 30 10g
> >
> > Other kernel configuration parameters:
> >
> >     zswap compressor : deflate-iaa
> >     zswap allocator   : zsmalloc
> >     vm.page-cluster   : 2,4
> >
> > IAA "compression verification" is disabled and the async poll acomp
> > interface is used in the iaa_crypto driver (the defaults with this
> > series).
> >
> >
> > Performance testing (usemem30):
> > ===============================
> >
> >  4K folios: deflate-iaa:
> >  =======================
> >
> >  -------------------------------------------------------------------------------
> >                 mm-unstable-10-16-2024  shrink_folio_list()  shrink_folio_list()
> >                                          batching of folios   batching of folios
> >  -------------------------------------------------------------------------------
> >  zswap compressor          deflate-iaa          deflate-iaa          deflate-iaa
> >  vm.compress-batchsize             n/a                    1                   32
> >  vm.page-cluster                     2                    2                    2
> >  -------------------------------------------------------------------------------
> >  Total throughput            4,470,466            5,770,824            6,363,045
> >            (KB/s)
> >  Average throughput            149,015              192,360              212,101
> >            (KB/s)
> >  elapsed time                   119.24               100.96                92.99
> >         (sec)
> >  sys time (sec)               2,819.29             2,168.08             1,970.79
> >
> >  -------------------------------------------------------------------------------
> >  memcg_high                    668,185              646,357              613,421
> >  memcg_swap_fail                     0                    0                    0
> >  zswpout                    62,991,796           58,275,673           53,070,201
> >  zswpin                            431                  415                  396
> >  pswpout                             0                    0                    0
> >  pswpin                              0                    0                    0
> >  thp_swpout                          0                    0                    0
> >  thp_swpout_fallback                 0                    0                    0
> >  pgmajfault                      3,137                3,085                3,440
> >  swap_ra                            99                  100                   95
> >  swap_ra_hit                        42                   44                   45
> >  -------------------------------------------------------------------------------
> >
> >
> >  16k/32/64k folios: deflate-iaa:
> >  ===============================
> >  All three large folio sizes 16k/32/64k were enabled to "always".
> >
> >  -------------------------------------------------------------------------------
> >                 mm-unstable-  zswap_store()      + shrink_folio_list()
> >                   10-16-2024    batching of         batching of folios
> >                                    pages in
> >                                large folios
> >  -------------------------------------------------------------------------------
> >  zswap compr     deflate-iaa     deflate-iaa          deflate-iaa
> >  vm.compress-            n/a             n/a         4          8             16
> >  batchsize
> >  vm.page-                  2               2         2          2              2
> >   cluster
> >  -------------------------------------------------------------------------------
> >  Total throughput   7,182,198   8,448,994    8,584,728    8,729,643
> 8,775,944
> >            (KB/s)
> >  Avg throughput       239,406     281,633      286,157      290,988      292,531
> >          (KB/s)
> >  elapsed time           85.04       77.84        77.03        75.18        74.98
> >          (sec)
> >  sys time (sec)      1,730.77    1,527.40     1,528.52     1,473.76     1,465.97
> >
> >  -------------------------------------------------------------------------------
> >  memcg_high           648,125     694,188      696,004      699,728      724,887
> >  memcg_swap_fail        1,550       2,540        1,627        1,577        1,517
> >  zswpout           57,606,876  56,624,450   56,125,082    55,999,42   57,352,204
> >  zswpin                   421         406          422          400          437
> >  pswpout                    0           0            0            0            0
> >  pswpin                     0           0            0            0            0
> >  thp_swpout                 0           0            0            0            0
> >  thp_swpout_fallback        0           0            0            0            0
> >  16kB-mthp_swpout_          0           0            0            0            0
> >           fallback
> >  32kB-mthp_swpout_          0           0            0            0            0
> >           fallback
> >  64kB-mthp_swpout_      1,550       2,539        1,627        1,577        1,517
> >           fallback
> >  pgmajfault             3,102       3,126        3,473        3,454        3,134
> >  swap_ra                  107         144          109          124          181
> >  swap_ra_hit               51          88           45           66          107
> >  ZSWPOUT-16kB               2           3            4            4            3
> >  ZSWPOUT-32kB               0           2            1            1            0
> >  ZSWPOUT-64kB       3,598,889   3,536,556    3,506,134    3,498,324
> 3,582,921
> >  SWPOUT-16kB                0           0            0            0            0
> >  SWPOUT-32kB                0           0            0            0            0
> >  SWPOUT-64kB                0           0            0            0            0
> >  -------------------------------------------------------------------------------
> >
> >
> >  2M folios: deflate-iaa:
> >  =======================
> >
> >  -------------------------------------------------------------------------------
> >                    mm-unstable-10-16-2024    zswap_store() batching of pages
> >                                                       in pmd-mappable folios
> >  -------------------------------------------------------------------------------
> >  zswap compressor             deflate-iaa                deflate-iaa
> >  vm.compress-batchsize                n/a                        n/a
> >  vm.page-cluster                        2                          2
> >  -------------------------------------------------------------------------------
> >  Total throughput               7,444,592                 8,916,349
> >            (KB/s)
> >  Average throughput               248,153                   297,211
> >            (KB/s)
> >  elapsed time                       86.29                     73.44
> >         (sec)
> >  sys time (sec)                  1,833.21                  1,418.58
> >
> >  -------------------------------------------------------------------------------
> >  memcg_high                        81,786                    89,905
> >  memcg_swap_fail                       82                       395
> >  zswpout                       58,874,092                57,721,884
> >  zswpin                               422                       458
> >  pswpout                                0                         0
> >  pswpin                                 0                         0
> >  thp_swpout                             0                         0
> >  thp_swpout_fallback                   82                       394
> >  pgmajfault                        14,864                    21,544
> >  swap_ra                           34,953                    53,751
> >  swap_ra_hit                       34,895                    53,660
> >  ZSWPOUT-2048kB                   114,815                   112,269
> >  SWPOUT-2048kB                          0                         0
> >  -------------------------------------------------------------------------------
> >
> > Since 4K folios account for ~0.4% of all zswapouts when pmd-mappable
> folios
> > are enabled for usemem30, we cannot expect much improvement from
> reclaim
> > batching.
> >
> >
> > Performance testing (Kernel compilation):
> > =========================================
> >
> > As mentioned earlier, for workloads that see a lot of swapout activity, we
> > can benefit from configuring 2 WQs per IAA device, with compress jobs from
> > all same-socket cores being distributed toothe wq.1 of all IAAs on the
> > socket, with the "global_wq" developed in this patch-series.
> >
> > Although this data includes IAA decompress batching, which will be
> > submitted as a separate RFC patch-series, I am listing it here to quantify
> > the benefit of distributing compress jobs among all IAAs. The kernel
> > compilation test with "allmodconfig" is able to quantify this well:
> >
> >
> >  4K folios: deflate-iaa: kernel compilation to quantify crypto patches
> >
> ==============================================================
> =======
> >
> >
> >  ------------------------------------------------------------------------------
> >                    IAA shrink_folio_list() compress batching and
> >                        swapin_readahead() decompress batching
> >
> >                                       1WQ      2WQ (distribute compress jobs)
> >
> >                         1 local WQ (wq.0)    1 local WQ (wq.0) +
> >                                   per IAA    1 global WQ (wq.1) per IAA
> >
> >  ------------------------------------------------------------------------------
> >  zswap compressor             deflate-iaa         deflate-iaa
> >  vm.compress-batchsize                 32                  32
> >  vm.page-cluster                        4                   4
> >  ------------------------------------------------------------------------------
> >  real_sec                          746.77              745.42
> >  user_sec                       15,732.66           15,738.85
> >  sys_sec                         5,384.14            5,247.86
> >  Max_Res_Set_Size_KB            1,874,432           1,872,640
> >
> >  ------------------------------------------------------------------------------
> >  zswpout                      101,648,460         104,882,982
> >  zswpin                        27,418,319          29,428,515
> >  pswpout                              213                  22
> >  pswpin                               207                   6
> >  pgmajfault                    21,896,616          23,629,768
> >  swap_ra                        6,054,409           6,385,080
> >  swap_ra_hit                    3,791,628           3,985,141
> >  ------------------------------------------------------------------------------
> >
> > The iaa_crypto wq stats will show almost the same number of compress
> calls
> > for wq.1 of all IAA devices. wq.0 will handle decompress calls exclusively.
> > We see a latency reduction of 2.5% by distributing compress jobs among all
> > IAA devices on the socket.
> >
> > I would greatly appreciate code review comments for the iaa_crypto driver
> > and mm patches included in this series!
> >
> > Thanks,
> > Kanchana
> >
> >
> >
> > Kanchana P Sridhar (13):
> >   crypto: acomp - Add a poll() operation to acomp_alg and acomp_req
> >   crypto: iaa - Add support for irq-less crypto async interface
> >   crypto: testmgr - Add crypto testmgr acomp poll support.
> >   mm: zswap: zswap_compress()/decompress() can submit, then poll an
> >     acomp_req.
> >   crypto: iaa - Make async mode the default.
> >   crypto: iaa - Disable iaa_verify_compress by default.
> >   crypto: iaa - Change cpu-to-iaa mappings to evenly balance cores to
> >     IAAs.
> >   crypto: iaa - Distribute compress jobs to all IAA devices on a NUMA
> >     node.
> >   mm: zswap: Config variable to enable compress batching in
> >     zswap_store().
> >   mm: zswap: Create multiple reqs/buffers in crypto_acomp_ctx if
> >     platform has IAA.
> >   mm: swap: Add IAA batch compression API
> >     swap_crypto_acomp_compress_batch().
> >   mm: zswap: Compress batching with Intel IAA in zswap_store() of large
> >     folios.
> >   mm: vmscan, swap, zswap: Compress batching of folios in
> >     shrink_folio_list().
> >
> >  crypto/acompress.c                         |   1 +
> >  crypto/testmgr.c                           |  70 +-
> >  drivers/crypto/intel/iaa/iaa_crypto_main.c | 467 +++++++++++--
> >  include/crypto/acompress.h                 |  18 +
> >  include/crypto/internal/acompress.h        |   1 +
> >  include/linux/fs.h                         |   2 +
> >  include/linux/mm.h                         |   8 +
> >  include/linux/writeback.h                  |   5 +
> >  include/linux/zswap.h                      | 106 +++
> >  kernel/sysctl.c                            |   9 +
> >  mm/Kconfig                                 |  12 +
> >  mm/page_io.c                               | 152 +++-
> >  mm/swap.c                                  |  15 +
> >  mm/swap.h                                  |  96 +++
> >  mm/swap_state.c                            | 115 +++
> >  mm/vmscan.c                                | 154 +++-
> >  mm/zswap.c                                 | 771 +++++++++++++++++++--
> >  17 files changed, 1870 insertions(+), 132 deletions(-)
> >
> >
> > base-commit: 817952b8be34aad40e07f6832fb9d1fc08961550
> > --
> > 2.27.0
> >
> >




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