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

["Huang, Ying" <ying.huang@intel.com>]

Hi, Barry,

Barry Song <21cnbao@gmail.com> writes:

> 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%

The data looks good.  Thanks!

Have you considered the situation that the large folio fails to be
allocated during swap-in?  It's possible because the memory may be very
fragmented.

> -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(-)

--
Best Regards,
Huang, Ying