[PATCH v3 0/3] Enable >0 order folio memory compaction

From: Zi Yan
Date: Fri Feb 02 2024 - 11:16:30 EST

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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 includes the fix[4] for
V2 and is on top of mm-everything-2024-01-29-07-19.

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 for default LRU (-no-mglru) and CONFIG_LRU_GEN are
shown at the bottom (on a 8-CPU (Intel Xeon E5-2650 v4 @ 2.20GHz) 16G VM).
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.

Changelog
===

>From V2 [3]:
1. Added missing free page count in fast isolation path. This fixed the
weird performance outcome.

>From V1 [2]:
1. Used folio_test_large() instead of folio_order() > 0. (per Matthew
Wilcox)

2. Fixed code rebase error. (per Baolin Wang)

3. Used list_split_init() instead of list_split(). (per Ryan Boberts)

4. Added free_pages_prepare_fpi_none() to avoid duplicate free page code
in compaction_free().

5. Dropped source page order sorting patch.

>From RFC [1]:
1. Enabled >0 order folio compaction in the first patch by splitting all
to-be-migrated folios. (per Huang, Ying)

2. Stopped isolating compound pages with order greater than cc->order
to avoid wasting effort, since cc->order gives a hint that no free pages
with order greater than it exist, thus migrating the compound pages will fail.
(per Baolin Wang)

3. Retained the folio check within lru lock. (per Baolin Wang)

4. Made isolate_freepages_block() generate order-sorted multi lists.
(per Johannes Weiner)

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.

Feel free to give comments and ask questions.

Thanks.

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

[1] https://lore.kernel.org/linux-mm/20230912162815.440749-1-zi.yan@xxxxxxxx/
[2] https://lore.kernel.org/linux-mm/20231113170157.280181-1-zi.yan@xxxxxxxx/
[3] https://lore.kernel.org/linux-mm/20240123034636.1095672-1-zi.yan@xxxxxxxx/
[4] https://lore.kernel.org/linux-mm/23BA8CC1-1014-4D09-9C33-938638E13C01@xxxxxxxxxx/

Zi Yan (3):
mm/compaction: enable compacting >0 order folios.
mm/compaction: add support for >0 order folio memory compaction.
mm/compaction: optimize >0 order folio compaction with free page
split.

mm/compaction.c | 219 ++++++++++++++++++++++++++++++++++--------------
mm/internal.h | 9 +-
mm/page_alloc.c | 6 ++
3 files changed, 170 insertions(+), 64 deletions(-)

--
2.43.0

Next message: Zi Yan: "[PATCH v3 1/3] mm/compaction: enable compacting >0 order folios."
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