Re: [PATCH v4 0/3] Enable >0 order folio memory compaction

[Zi Yan]

On 12 Feb 2024, at 13:44, Yu Zhao wrote:

> On Mon, Feb 12, 2024 at 9:35 AM Zi Yan <zi.yan@xxxxxxxx> wrote:
>>
>> From: Zi Yan <ziy@xxxxxxxxxx>
>>
>> Hi all,
>>
>> This patchset enables >0 order folio memory compaction, which is one of
>> the prerequisitions for large folio support[1]. It is on top of
>> mm-everything-2024-02-10-00-56.
>>
>> I am aware of that split free pages is necessary for folio
>> migration in compaction, since if >0 order free pages are never split
>> and no order-0 free page is scanned, compaction will end prematurely due
>> to migration returns -ENOMEM. Free page split becomes a must instead of
>> an optimization.
>>
>> lkp ncompare results (on a 8-CPU (Intel Xeon E5-2650 v4 @2.20GHz) 16G VM)
>> for default LRU (-no-mglru) and CONFIG_LRU_GEN are shown at the bottom,
>> copied from V3[4], since V4 is only a code refactoring of V3.
>> In sum, most of vm-scalability applications do not see performance
>> change, and the others see ~4% to ~26% performance boost under default LRU
>> and ~2% to ~6% performance boost under CONFIG_LRU_GEN.
>
> Suren has been testing 64KB THP on Android and seeing regressions
> under memory pressure (a significant portion of client devices are
> always under memory pressure). Hopefully this series will help.
>
> I threw this series into some stress tests we have with both 64KB and
> 2MB THP enabled and didn't see any obvious problems.
>
> Tested-by: Yu Zhao <yuzhao@xxxxxxxxxx>

Thank you for the testing.
>
>> Overview
>> ===
>>
>> To support >0 order folio compaction, the patchset changes how free pages used
>> for migration are kept during compaction. Free pages used to be split into
>> order-0 pages that are post allocation processed (i.e., PageBuddy flag cleared,
>> page order stored in page->private is zeroed, and page reference is set to 1).
>> Now all free pages are kept in a MAX_ORDER+1 array of page lists based
>> on their order without post allocation process. When migrate_pages() asks for
>> a new page, one of the free pages, based on the requested page order, is
>> then processed and given out.
>
> And THP <2MB would need this feature (spell it out).

Will add this.
>
>
>
>> vm-scalability results on CONFIG_LRU_GEN
>> ===
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/mmap-xread-seq-mt/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19+
>>   6.8.0-rc1-split-folio-in-compaction+
>>   6.8.0-rc1-folio-migration-in-compaction+
>>   6.8.0-rc1-folio-migration-free-page-split+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>   15107616            +3.2%   15590339            +1.3%   15297619            +3.0%   15567998        vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19+
>>   6.8.0-rc1-split-folio-in-compaction+
>>   6.8.0-rc1-folio-migration-in-compaction+
>>   6.8.0-rc1-folio-migration-free-page-split+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>   12611785            +1.8%   12832919            +0.9%   12724223            +1.6%   12812682        vm-scalability.throughput
>>
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/lru-file-readtwice/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19+
>>   6.8.0-rc1-split-folio-in-compaction+
>>   6.8.0-rc1-folio-migration-in-compaction+
>>   6.8.0-rc1-folio-migration-free-page-split+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>    9833393            +5.7%   10390190            +3.0%   10126606            +5.9%   10408804        vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/lru-file-mmap-read/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19+
>>   6.8.0-rc1-split-folio-in-compaction+
>>   6.8.0-rc1-folio-migration-in-compaction+
>>   6.8.0-rc1-folio-migration-free-page-split+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>    7034709 ±  3%      +2.9%    7241429            +3.2%    7256680 ±  2%      +3.9%    7308375        vm-scalability.throughput
>>
>>
>>
>> vm-scalability results on default LRU (with -no-mglru suffix)
>> ===
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/mmap-xread-seq-mt/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19-no-mglru+
>>   6.8.0-rc1-split-folio-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-free-page-split-no-mglru+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>   14401491            +3.7%   14940270            +2.4%   14748626            +4.0%   14975716        vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19-no-mglru+
>>   6.8.0-rc1-split-folio-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-free-page-split-no-mglru+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>   11407497            +5.1%   11989632            -0.5%   11349272            +4.8%   11957423        vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq-mt/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19-no-mglru+
>>   6.8.0-rc1-split-folio-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-free-page-split-no-mglru+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>   11348474            +3.3%   11719453            -1.2%   11208759            +3.7%   11771926        vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/lru-file-readtwice/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19-no-mglru+
>>   6.8.0-rc1-split-folio-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-free-page-split-no-mglru+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>    8065614 ±  3%      +7.7%    8686626 ±  2%      +5.0%    8467577 ±  4%     +11.8%    9016077 ±  2%  vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>>   gcc-13/defconfig/debian/300s/qemu-vm/lru-file-mmap-read/vm-scalability
>>
>> commit:
>>   6.8.0-rc1-mm-everything-2024-01-29-07-19-no-mglru+
>>   6.8.0-rc1-split-folio-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-in-compaction-no-mglru+
>>   6.8.0-rc1-folio-migration-free-page-split-no-mglru+
>>
>> 6.8.0-rc1-mm-eve 6.8.0-rc1-split-folio-in-co 6.8.0-rc1-folio-migration-i 6.8.0-rc1-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>>          %stddev     %change         %stddev     %change         %stddev     %change         %stddev
>>              \          |                \          |                \          |                \
>>    6438422 ±  2%     +27.5%    8206734 ±  2%     +10.6%    7118390           +26.2%    8127192 ±  4%  vm-scalability.throughput
>
> Thanks for the data! Based on the above:
>
> Test case                          default   MGLRU     Change
> =============================================================
> mmap-xread-seq-mt/vm-scalability   14975716  15567998  +4%
> mmap-pread-seq/vm-scalability      11957423  12812682  +7%
> mmap-pread-seq-mt/vm-scalability   11771926  unavail   N/A
> lru-file-readtwice/vm-scalability  9016077   10408804  +15%
> lru-file-mmap-read/vm-scalability  8127192   7308375   -10%
>
> So it seems that MGLRU regressed for the last test. I'll find someone
> on our team to take a look.

Thanks.

--
Best Regards,
Yan, Zi

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