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Message-ID: <87msl9i4lw.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Mon, 19 Aug 2024 11:16:59 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
Cc: <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
<hannes@...xchg.org>, <yosryahmed@...gle.com>, <nphamcs@...il.com>,
<ryan.roberts@....com>, <21cnbao@...il.com>,
<akpm@...ux-foundation.org>, <nanhai.zou@...el.com>,
<wajdi.k.feghali@...el.com>, <vinodh.gopal@...el.com>
Subject: Re: [PATCH v4 0/4] mm: ZSWAP swap-out of mTHP folios
Kanchana P Sridhar <kanchana.p.sridhar@...el.com> writes:
[snip]
>
> Performance Testing:
> ====================
> Testing of this patch-series was done with the v6.11-rc3 mainline, without
> and with this patch-series, on an Intel Sapphire Rapids server,
> dual-socket 56 cores per socket, 4 IAA devices per socket.
>
> The system has 503 GiB RAM, with a 4G SSD as the backing swap device for
> ZSWAP. Core frequency was fixed at 2500MHz.
>
> The vm-scalability "usemem" test was run in a cgroup whose memory.high
> was fixed. Following a similar methodology as in Ryan Roberts'
> "Swap-out mTHP without splitting" series [2], 70 usemem processes were
> run, each allocating and writing 1G of memory:
>
> usemem --init-time -w -O -n 70 1g
>
> Since I was constrained to get the 70 usemem processes to generate
> swapout activity with the 4G SSD, I ended up using different cgroup
> memory.high fixed limits for the experiments with 64K mTHP and 2M THP:
>
> 64K mTHP experiments: cgroup memory fixed at 60G
> 2M THP experiments : cgroup memory fixed at 55G
>
> The vm/sysfs stats included after the performance data provide details
> on the swapout activity to SSD/ZSWAP.
>
> Other kernel configuration parameters:
>
> ZSWAP Compressor : LZ4, DEFLATE-IAA
> ZSWAP Allocator : ZSMALLOC
> SWAP page-cluster : 2
>
> In the experiments where "deflate-iaa" is used as the ZSWAP compressor,
> IAA "compression verification" is enabled. 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.
>
> Throughput reported by usemem and perf sys time for running the test
> are as follows, averaged across 3 runs:
>
> 64KB mTHP (cgroup memory.high set to 60G):
> ==========================================
> ------------------------------------------------------------------
> | | | | |
> |Kernel | mTHP SWAP-OUT | Throughput | Improvement|
> | | | KB/s | |
> |--------------------|-------------------|------------|------------|
> |v6.11-rc3 mainline | SSD | 335,346 | Baseline |
> |zswap-mTHP-Store | ZSWAP lz4 | 271,558 | -19% |
zswap throughput is worse than ssd swap? This doesn't look right.
> |zswap-mTHP-Store | ZSWAP deflate-iaa | 388,154 | 16% |
> |------------------------------------------------------------------|
> | | | | |
> |Kernel | mTHP SWAP-OUT | Sys time | Improvement|
> | | | sec | |
> |--------------------|-------------------|------------|------------|
> |v6.11-rc3 mainline | SSD | 91.37 | Baseline |
> |zswap-mTHP=Store | ZSWAP lz4 | 265.43 | -191% |
> |zswap-mTHP-Store | ZSWAP deflate-iaa | 235.60 | -158% |
> ------------------------------------------------------------------
>
> -----------------------------------------------------------------------
> | VMSTATS, mTHP ZSWAP/SSD stats| v6.11-rc3 | zswap-mTHP | zswap-mTHP |
> | | mainline | Store | Store |
> | | | lz4 | deflate-iaa |
> |-----------------------------------------------------------------------|
> | pswpin | 0 | 0 | 0 |
> | pswpout | 174,432 | 0 | 0 |
> | zswpin | 703 | 534 | 721 |
> | zswpout | 1,501 | 1,491,654 | 1,398,805 |
It appears that the number of swapped pages for zswap is much larger
than that of SSD swap. Why? I guess this is why zswap throughput is
worse.
> |-----------------------------------------------------------------------|
> | thp_swpout | 0 | 0 | 0 |
> | thp_swpout_fallback | 0 | 0 | 0 |
> | pgmajfault | 3,364 | 3,650 | 3,431 |
> |-----------------------------------------------------------------------|
> | hugepages-64kB/stats/zswpout | | 63,200 | 63,244 |
> |-----------------------------------------------------------------------|
> | hugepages-64kB/stats/swpout | 10,902 | 0 | 0 |
> -----------------------------------------------------------------------
>
[snip]
--
Best Regards,
Huang, Ying
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