[PATCH RFC v2 0/2] mTHP-friendly compression in zsmalloc and zram based on multi-pages

[Barry Song <21cnbao@gmail.com>]

From: Barry Song <v-songbaohua@oppo.com>

When large folios are compressed at a larger granularity, we observe
a notable reduction in CPU usage and a significant improvement in
compression ratios.

mTHP's ability to be swapped out without splitting and swapped back in
as a whole allows compression and decompression at larger granularities.

This patchset enhances zsmalloc and zram by adding support for dividing
large folios into multi-page blocks, typically configured with a
2-order granularity. Without this patchset, a large folio is always
divided into `nr_pages` 4KiB blocks.

The granularity can be set using the `ZSMALLOC_MULTI_PAGES_ORDER`
setting, where the default of 2 allows all anonymous THP to benefit.

Examples include:
* A 16KiB large folio will be compressed and stored as a single 16KiB
  block.
* A 64KiB large folio will be compressed and stored as four 16KiB
  blocks.

For example, swapping out and swapping in 100MiB of typical anonymous
data 100 times (with 16KB mTHP enabled) using zstd yields the following
results:

                        w/o patches        w/ patches
swap-out time(ms)       68711              49908
swap-in time(ms)        30687              20685
compression ratio       20.49%             16.9%

-v2:
 While it is not mature yet, I know some people are waiting for
 an update :-)
 * Fixed some stability issues.
 * rebase againest the latest mm-unstable.
 * Set default order to 2 which benefits all anon mTHP.
 * multipages ZsPageMovable is not supported yet.

Tangquan Zheng (2):
  mm: zsmalloc: support objects compressed based on multiple pages
  zram: support compression at the granularity of multi-pages

 drivers/block/zram/Kconfig    |   9 +
 drivers/block/zram/zcomp.c    |  17 +-
 drivers/block/zram/zcomp.h    |  12 +-
 drivers/block/zram/zram_drv.c | 450 +++++++++++++++++++++++++++++++---
 drivers/block/zram/zram_drv.h |  45 ++++
 include/linux/zsmalloc.h      |  10 +-
 mm/Kconfig                    |  18 ++
 mm/zsmalloc.c                 | 232 +++++++++++++-----
 8 files changed, 699 insertions(+), 94 deletions(-)

-- 
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