linux-kernel - Re: [PATCH v1 0/4] Enable >0 order folio memory compaction

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Date:   Tue, 21 Nov 2023 17:11:36 +0000
From:   Ryan Roberts <ryan.roberts@....com>
To:     Zi Yan <ziy@...dia.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Huang, Ying" <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        "Yin, Fengwei" <fengwei.yin@...el.com>,
        Yu Zhao <yuzhao@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Kemeng Shi <shikemeng@...weicloud.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Rohan Puri <rohan.puri15@...il.com>,
        Mcgrof Chamberlain <mcgrof@...nel.org>,
        Adam Manzanares <a.manzanares@...sung.com>,
        "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Subject: Re: [PATCH v1 0/4] Enable >0 order folio memory compaction

On 21/11/2023 16:45, Zi Yan wrote:
> On 21 Nov 2023, at 10:46, Ryan Roberts wrote:
> 
>>>
>>> vm-scalability results
>>> ===
>>>
>>> =========================================================================================
>>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>>   gcc-13/defconfig/debian/300s/qemu-vm/mmap-xread-seq-mt/vm-scalability
>>>
>>> commit:
>>>   6.6.0-rc4-mm-everything-2023-10-21-02-40+
>>>   6.6.0-rc4-split-folio-in-compaction+
>>>   6.6.0-rc4-folio-migration-in-compaction+
>>>   6.6.0-rc4-folio-migration-free-page-split+
>>>   6.6.0-rc4-folio-migration-free-page-split-sort-src+
>>>
>>> 6.6.0-rc4-mm-eve 6.6.0-rc4-split-folio-in-co 6.6.0-rc4-folio-migration-i 6.6.0-rc4-folio-migration-f 6.6.0-rc4-folio-migration-f
>>> ---------------- --------------------------- --------------------------- --------------------------- ---------------------------
>>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>>              \          |                \          |                \          |                \          |                \
>>>   12896955            +2.7%   13249322            -4.0%   12385175 ±  5%      +1.1%   13033951            -0.4%   12845698        vm-scalability.throughput
>>
>> Hi Zi,
>>
>> Are you able to add any commentary to these results as I'm struggling to
>> interpret them; Is a positive or negative change better (are they times or
>> rates?). What are the stddev values? The title suggests percent but the values
>> are huge - I'm trying to understand what the error bars look like - are the
>> swings real or noise?
> 
> The metric is vm-scalability.throughput, so the larger the better. Some %stddev
> are not present since they are too small. For 6.6.0-rc4-folio-migration-in-compaction+,
> %stddev is greater than %change, so the change might be noise.

Ahh got it - thanks!

> 
> Also, I talked to DavidH in last THP Cabal meeting about this. He suggested that
> there are a lot of noise in vm-scalability like what I have here and I should
> run more iterations and on bare metal. I am currently rerun them on a baremetal
> and more iterations on the existing VM and report the results later. Please
> note that the runs really take some time.

Ahh ok, I'll wait for the bare metal numbers and will disregard these for now.
Thanks!

> 
> In addition, I will find other fragmentation-related benchmarks, so we can see
> the impact on memory fragmentation.
> 
> --
> Best Regards,
> Yan, Zi