| #
69bad215 |
| 01-Oct-2024 |
Kanchana P Sridhar <[email protected]> |
mm: define obj_cgroup_get() if CONFIG_MEMCG is not defined
Patch series "mm: zswap swap-out of large folios", v10.
This patch series enables zswap_store() to accept and store large folios.
The mos
mm: define obj_cgroup_get() if CONFIG_MEMCG is not defined
Patch series "mm: zswap swap-out of large folios", v10.
This patch series enables zswap_store() to accept and store large folios.
The most significant contribution in this series is from the earlier RFC
submitted by Ryan Roberts [1]. Ryan's original RFC has been migrated to
mm-unstable as of 9-30-2024 in patch 6 of this series, and adapted based
on code review comments received for the current patch-series.
[1]: [RFC PATCH v1] mm: zswap: Store large folios without splitting
https://lore.kernel.org/linux-mm/[email protected]/T/#u
The first few patches do the prep work for supporting large folios in
zswap_store. Patch 6 provides the main functionality to swap-out large
folios in zswap. Patch 7 adds sysfs per-order hugepages "zswpout"
counters that get incremented upon successful zswap_store of large folios,
and also updates the documentation for this:
/sys/kernel/mm/transparent_hugepage/hugepages-*kB/stats/zswpout
This patch series is a prerequisite for zswap compress batching of large
folio swap-out and decompress batching of swap-ins based on
swapin_readahead(), using Intel IAA hardware acceleration, which we would
like to submit in subsequent patch-series, with performance improvement
data.
Thanks to Ying Huang for pre-posting review feedback and suggestions!
Thanks also to Nhat, Yosry, Johannes, Barry, Chengming, Usama, Ying and
Matthew for their helpful feedback, code/data reviews and suggestions!
Co-development signoff request:
===============================
I would like to thank Ryan Roberts for his original RFC [1] and request
his co-developer signoff on patch 6 in this series. Thanks Ryan!
System setup for testing:
=========================
Testing of this patch series was done with mm-unstable as of 9-27-2024,
commit de2fbaa6d9c3576ec7133ed02a370ec9376bf000 (without this patch-series)
and mm-unstable 9-30-2024 commit c121617e3606be6575cdacfdb63cc8d67b46a568
(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 compressors : zstd, deflate-iaa
zswap allocator : zsmalloc
vm.page-cluster : 2
In the experiments where "deflate-iaa" is used as the zswap compressor,
IAA "compression verification" is enabled by default
(cat /sys/bus/dsa/drivers/crypto/verify_compress). Hence each IAA
compression will be decompressed internally by the "iaa_crypto" driver, the
crc-s returned by the hardware will be compared and errors reported in case
of mismatches. Thus "deflate-iaa" helps ensure better data integrity as
compared to the software compressors, and the experimental data listed
below is with verify_compress set to "1".
Metrics reporting methodology:
==============================
Total and average throughput are derived from the individual 30 processes'
throughputs reported by usemem. elapsed/sys times are measured with perf.
All percentage changes are "new" vs. "old"; hence a positive value
denotes an increase in the metric, whether it is throughput or latency,
and a negative value denotes a reduction in the metric. Positive throughput
change percentages and negative latency change percentages denote improvements.
The vm stats and sysfs hugepages stats included with the performance data
provide details on the swapout activity to zswap/swap device.
Testing labels used in data summaries:
======================================
The data refers to these test configurations and the before/after
comparisons that they do:
before-case1:
-------------
mm-unstable 9-27-2024, CONFIG_THP_SWAP=N (compares zswap 4K vs. zswap 64K)
In this scenario, CONFIG_THP_SWAP=N results in 64K/2M folios to be split
into 4K folios that get processed by zswap.
before-case2:
-------------
mm-unstable 9-27-2024, CONFIG_THP_SWAP=Y (compares SSD swap large folios vs. zswap large folios)
In this scenario, CONFIG_THP_SWAP=Y results in zswap rejecting large
folios, which will then be stored by the SSD swap device.
after:
------
v10 of this patch-series, CONFIG_THP_SWAP=Y
The "after" is CONFIG_THP_SWAP=Y and v10 of this patch-series, that results
in 64K/2M folios to not be split, and to be processed by zswap_store.
Regression Testing:
===================
I ran vm-scalability usemem without large folios, i.e., only 4K folios with
mm-unstable and this patch-series. The main goal was to make sure that
there is no functional or performance regression wrt the earlier zswap
behavior for 4K folios, now that 4K folios will be processed by the new
zswap_store() code.
The data indicates there is no significant regression.
-------------------------------------------------------------------------------
4K folios:
==========
zswap compressor zstd zstd zstd zstd v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 4,793,363 4,880,978 4,853,074 1% -1%
Average throughput (KB/s) 159,778 162,699 161,769 1% -1%
elapsed time (sec) 130.14 123.17 126.29 -3% 3%
sys time (sec) 3,135.53 2,985.64 3,083.18 -2% 3%
memcg_high 446,826 444,626 452,930
memcg_swap_fail 0 0 0
zswpout 48,932,107 48,931,971 48,931,820
zswpin 383 386 397
pswpout 0 0 0
pswpin 0 0 0
thp_swpout 0 0 0
thp_swpout_fallback 0 0 0
64kB-mthp_swpout_fallback 0 0 0
pgmajfault 3,063 3,077 3,479
swap_ra 93 94 96
swap_ra_hit 47 47 50
ZSWPOUT-64kB n/a n/a 0
SWPOUT-64kB 0 0 0
-------------------------------------------------------------------------------
Performance Testing:
====================
We list the data for 64K folios with before/after data per-compressor,
followed by the same for 2M pmd-mappable folios.
-------------------------------------------------------------------------------
64K folios: zstd:
=================
zswap compressor zstd zstd zstd zstd v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 5,222,213 1,076,611 6,159,776 18% 472%
Average throughput (KB/s) 174,073 35,887 205,325 18% 472%
elapsed time (sec) 120.50 347.16 108.33 -10% -69%
sys time (sec) 2,930.33 248.16 2,549.65 -13% 927%
memcg_high 416,773 552,200 465,874
memcg_swap_fail 3,192,906 1,293 1,012
zswpout 48,931,583 20,903 48,931,218
zswpin 384 363 410
pswpout 0 40,778,448 0
pswpin 0 16 0
thp_swpout 0 0 0
thp_swpout_fallback 0 0 0
64kB-mthp_swpout_fallback 3,192,906 1,293 1,012
pgmajfault 3,452 3,072 3,061
swap_ra 90 87 107
swap_ra_hit 42 43 57
ZSWPOUT-64kB n/a n/a 3,057,173
SWPOUT-64kB 0 2,548,653 0
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
64K folios: deflate-iaa:
========================
zswap compressor deflate-iaa deflate-iaa deflate-iaa deflate-iaa v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 5,652,608 1,089,180 7,189,778 27% 560%
Average throughput (KB/s) 188,420 36,306 239,659 27% 560%
elapsed time (sec) 102.90 343.35 87.05 -15% -75%
sys time (sec) 2,246.86 213.53 1,864.16 -17% 773%
memcg_high 576,104 502,907 642,083
memcg_swap_fail 4,016,117 1,407 1,478
zswpout 61,163,423 22,444 57,798,716
zswpin 401 368 454
pswpout 0 40,862,080 0
pswpin 0 20 0
thp_swpout 0 0 0
thp_swpout_fallback 0 0 0
64kB-mthp_swpout_fallback 4,016,117 1,407 1,478
pgmajfault 3,063 3,153 3,122
swap_ra 96 93 156
swap_ra_hit 46 45 83
ZSWPOUT-64kB n/a n/a 3,611,032
SWPOUT-64kB 0 2,553,880 0
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
2M folios: zstd:
================
zswap compressor zstd zstd zstd zstd v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 5,895,500 1,109,694 6,484,224 10% 484%
Average throughput (KB/s) 196,516 36,989 216,140 10% 484%
elapsed time (sec) 108.77 334.28 106.33 -2% -68%
sys time (sec) 2,657.14 94.88 2,376.13 -11% 2404%
memcg_high 64,200 66,316 56,898
memcg_swap_fail 101,182 70 27
zswpout 48,931,499 36,507 48,890,640
zswpin 380 379 377
pswpout 0 40,166,400 0
pswpin 0 0 0
thp_swpout 0 78,450 0
thp_swpout_fallback 101,182 70 27
2MB-mthp_swpout_fallback 0 0 27
pgmajfault 3,067 3,417 3,311
swap_ra 91 90 854
swap_ra_hit 45 45 810
ZSWPOUT-2MB n/a n/a 95,459
SWPOUT-2MB 0 78,450 0
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
2M folios: deflate-iaa:
=======================
zswap compressor deflate-iaa deflate-iaa deflate-iaa deflate-iaa v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 6,286,587 1,126,785 7,073,464 13% 528%
Average throughput (KB/s) 209,552 37,559 235,782 13% 528%
elapsed time (sec) 96.19 333.03 85.79 -11% -74%
sys time (sec) 2,141.44 99.96 1,826.67 -15% 1727%
memcg_high 99,253 64,666 79,718
memcg_swap_fail 129,074 53 165
zswpout 61,312,794 28,321 56,045,120
zswpin 383 406 403
pswpout 0 40,048,128 0
pswpin 0 0 0
thp_swpout 0 78,219 0
thp_swpout_fallback 129,074 53 165
2MB-mthp_swpout_fallback 0 0 165
pgmajfault 3,430 3,077 31,468
swap_ra 91 103 84,373
swap_ra_hit 47 46 84,317
ZSWPOUT-2MB n/a n/a 109,229
SWPOUT-2MB 0 78,219 0
-------------------------------------------------------------------------------
And finally, this is a comparison of deflate-iaa vs. zstd with v10 of this
patch-series:
---------------------------------------------
zswap_store large folios v10
Impr w/ deflate-iaa vs. zstd
64K folios 2M folios
---------------------------------------------
Throughput (KB/s) 17% 9%
elapsed time (sec) -20% -19%
sys time (sec) -27% -23%
---------------------------------------------
Conclusions based on the performance results:
=============================================
v10 wrt before-case1:
---------------------
We see significant improvements in throughput, elapsed and sys time for
zstd and deflate-iaa, when comparing before-case1 (THP_SWAP=N) vs. after
(THP_SWAP=Y) with zswap_store large folios.
v10 wrt before-case2:
---------------------
We see even more significant improvements in throughput and elapsed time
for zstd and deflate-iaa, when comparing before-case2 (large-folio-SSD)
vs. after (large-folio-zswap). The sys time increases with
large-folio-zswap as expected, due to the CPU compression time
vs. asynchronous disk write times, as pointed out by Ying and Yosry.
In before-case2, when zswap does not store large folios, only allocations
and cgroup charging due to 4K folio zswap stores count towards the cgroup
memory limit. However, in the after scenario, with the introduction of
zswap_store() of large folios, there is an added component of the zswap
compressed pool usage from large folio stores from potentially all 30
processes, that gets counted towards the memory limit. As a result, we see
higher swapout activity in the "after" data.
Summary:
========
The v10 data presented above shows that zswap_store of large folios
demonstrates good throughput/performance improvements compared to
conventional SSD swap of large folios with a sufficiently large 525G SSD
swap device. Hence, it seems reasonable for zswap_store to support large
folios, so that further performance improvements can be implemented.
In the experimental setup used in this patchset, we have enabled IAA
compress verification to ensure additional hardware data integrity CRC
checks not currently done by the software compressors. We see good
throughput/latency improvements with deflate-iaa vs. zstd with zswap_store
of large folios.
Some of the ideas for further reducing latency that have shown promise in
our experiments, are:
1) IAA compress/decompress batching.
2) Distributing compress jobs across all IAA devices on the socket.
The tests run for this patchset are using only 1 IAA device per core, that
avails of 2 compress engines on the device. In our experiments with IAA
batching, we distribute compress jobs from all cores to the 8 compress
engines available per socket. We further compress the pages in each folio
in parallel in the accelerator. As a result, we improve compress latency
and reclaim throughput.
In decompress batching, we use swapin_readahead to generate a prefetch
batch of 4K folios that we decompress in parallel in IAA.
------------------------------------------------------------------------------
IAA compress/decompress batching
Further improvements wrt v10 zswap_store Sequential
subpage store using "deflate-iaa":
"deflate-iaa" Batching "deflate-iaa-canned" [2] Batching
Additional Impr Additional Impr
64K folios 2M folios 64K folios 2M folios
------------------------------------------------------------------------------
Throughput (KB/s) 19% 43% 26% 55%
elapsed time (sec) -5% -14% -10% -21%
sys time (sec) 4% -7% -4% -18%
------------------------------------------------------------------------------
With zswap IAA compress/decompress batching, we are able to demonstrate
significant performance improvements and memory savings in server
scalability experiments in highly contended system scenarios under
significant memory pressure; as compared to software compressors. We hope
to submit this work in subsequent patch series. The current patch-series is
a prequisite for these future submissions.
[1] https://lore.kernel.org/linux-mm/[email protected]/T/#u
[2] https://patchwork.kernel.org/project/linux-crypto/cover/[email protected]/
This patch (of 6):
This resolves an issue with obj_cgroup_get() not being defined if
CONFIG_MEMCG is not defined.
Before this patch, we would see build errors if obj_cgroup_get() is called
from code that is agnostic of CONFIG_MEMCG.
The zswap_store() changes for large folios in subsequent commits will
require the use of obj_cgroup_get() in zswap code that falls into this
category.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kanchana P Sridhar <[email protected]>
Reviewed-by: Nhat Pham <[email protected]>
Reviewed-by: Yosry Ahmed <[email protected]>
Reviewed-by: Chengming Zhou <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Usama Arif <[email protected]>
Cc: Wajdi Feghali <[email protected]>
Cc: "Zou, Nanhai" <[email protected]>
Cc: Barry Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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