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

From: Barry Song <21cnbao@gmail.com>
To: akpm@linux-foundation.org, minchan@kernel.org,
	senozhatsky@chromium.org, linux-block@vger.kernel.org,
	axboe@kernel.dk, linux-mm@kvack.org
Cc: terrelln@fb.com, chrisl@kernel.org, david@redhat.com,
	kasong@tencent.com, yuzhao@google.com, yosryahmed@google.com,
	nphamcs@gmail.com, willy@infradead.org, hannes@cmpxchg.org,
	ying.huang@intel.com, surenb@google.com,
	wajdi.k.feghali@intel.com, kanchana.p.sridhar@intel.com,
	corbet@lwn.net, zhouchengming@bytedance.com,
	Barry Song <v-songbaohua@oppo.com>
Subject: [PATCH RFC 0/2] mTHP-friendly compression in zsmalloc and zram based on multi-pages
Date: Thu, 28 Mar 2024 10:48:14 +1300	[thread overview]
Message-ID: <20240327214816.31191-1-21cnbao@gmail.com> (raw)

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

mTHP is generally considered to potentially waste memory due to fragmentation,
but it may also serve as a source of memory savings.
When large folios are compressed at a larger granularity, we observe a remarkable
decrease in CPU utilization and a significant improvement in compression ratios.

The following data illustrates the time and compressed data for typical anonymous
pages gathered from Android phones.

granularity   orig_data_size   compr_data_size   time(us)
4KiB-zstd      1048576000       246876055        50259962
64KiB-zstd     1048576000       199763892        18330605

Due to mTHP's ability to be swapped out without splitting[1] and swapped in as a
whole[2], it enables compression and decompression to be performed at larger
granularities.

This patchset enhances zsmalloc and zram by introducing support for dividing large
folios into multi-pages, typically configured with a 4-order granularity. Here are
concrete examples:

* If a large folio's size is 32KiB, it will still be compressed and stored at a 4KiB
  granularity.
* If a large folio's size is 64KiB, it will be compressed and stored as a single 64KiB
  block.
* If a large folio's size is 128KiB, it will be compressed and stored as two 64KiB
  multi-pages.

Without the patchset, a large folio is always divided into nr_pages 4KiB blocks.

The granularity can be configured using the ZSMALLOC_MULTI_PAGES_ORDER setting.

[1] https://lore.kernel.org/linux-mm/20240327144537.4165578-1-ryan.roberts@arm.com/
[2] https://lore.kernel.org/linux-mm/20240304081348.197341-1-21cnbao@gmail.com/

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    |  23 ++-
 drivers/block/zram/zcomp.h    |  12 +-
 drivers/block/zram/zram_drv.c | 372 +++++++++++++++++++++++++++++++---
 drivers/block/zram/zram_drv.h |  21 ++
 include/linux/zsmalloc.h      |  10 +-
 mm/Kconfig                    |  18 ++
 mm/zsmalloc.c                 | 215 +++++++++++++++-----
 8 files changed, 586 insertions(+), 94 deletions(-)

-- 
2.34.1