mm/zswap: use only one pool in zswap

Zswap uses 32 pools to workaround the locking scalability problem in zswap
backends (mainly zsmalloc nowadays), which brings its own problems like
memory waste and more memory fragmentation.

Testing results show that we can have near performance with only one pool
in zswap after changing zsmalloc to use per-size_class lock instead of
pool spinlock.

Testing kernel build (make bzImage -j32) on tmpfs with memory.max=1GB, and
zswap shrinker enabled with 10GB swapfile on ext4.

                                real    user    sys
6.10.0-rc3                      138.18  1241.38 1452.73
6.10.0-rc3-onepool              149.45  1240.45 1844.69
6.10.0-rc3-onepool-perclass     138.23  1242.37 1469.71

And do the same testing using zbud, which shows a little worse performance
as expected since we don't do any locking optimization for zbud.  I think
it's acceptable since zsmalloc became a lot more popular than other
backends, and we may want to support only zsmalloc in the future.

                                real    user    sys
6.10.0-rc3-zbud			138.23  1239.58 1430.09
6.10.0-rc3-onepool-zbud		139.64  1241.37 1516.59

[chengming.zhou@linux.dev: fix error handling in zswap_pool_create(), per Dan Carpenter]
  Link: https://lkml.kernel.org/r/20240621-zsmalloc-lock-mm-everything-v2-2-d30e9cd2b793@linux.dev
[chengming.zhou@linux.dev: fix error handling again in zswap_pool_create(), per Yosry]
  Link: https://lkml.kernel.org/r/20240625-zsmalloc-lock-mm-everything-v3-2-ad941699cb61@linux.dev
Link: https://lkml.kernel.org/r/20240617-zsmalloc-lock-mm-everything-v1-2-5e5081ea11b3@linux.dev
Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions