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

[Zi Yan]

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.

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.

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

--
Best Regards,
Yan, Zi

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