Re: + mm-zswap-add-pool-shrinking-mechanism.patch added to mm-unstable branch

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (23/06/12 13:51), Andrew Morton wrote:
> Subject: mm: zswap: add pool shrinking mechanism
> Date: Mon, 12 Jun 2023 11:38:09 +0200
> 
> Patch series "mm: zswap: move writeback LRU from zpool to zswap", v3.
> 
> This series aims to improve the zswap reclaim mechanism by reorganizing
> the LRU management. In the current implementation, the LRU is maintained
> within each zpool driver, resulting in duplicated code across the three
> drivers. The proposed change consists in moving the LRU management from
> the individual implementations up to the zswap layer.
> 
> The primary objective of this refactoring effort is to simplify the
> codebase. By unifying the reclaim loop and consolidating LRU handling
> within zswap, we can eliminate redundant code and improve
> maintainability. Additionally, this change enables the reclamation of
> stored pages in their actual LRU order. Presently, the zpool drivers
> link backing pages in an LRU, causing compressed pages with different
> LRU positions to be written back simultaneously.
> 
> The series consists of several patches. The first patch implements the
> LRU and the reclaim loop in zswap, but it is not used yet because all
> three driver implementations are marked as zpool_evictable.
> The following three commits modify each zpool driver to be not
> zpool_evictable, allowing the use of the reclaim loop in zswap.
> As the drivers removed their shrink functions, the zpool interface is
> then trimmed by removing zpool_evictable, zpool_ops, and zpool_shrink.
> Finally, the code in zswap is further cleaned up by simplifying the
> writeback function and removing the now unnecessary zswap_header.
> 
> 
> This patch (of 7):
> 
> Each zpool driver (zbud, z3fold and zsmalloc) implements its own shrink
> function, which is called from zpool_shrink.  However, with this commit, a
> unified shrink function is added to zswap.  The ultimate goal is to
> eliminate the need for zpool_shrink once all zpool implementations have
> dropped their shrink code.
> 
> To ensure the functionality of each commit, this change focuses solely on
> adding the mechanism itself.  No modifications are made to the backends,
> meaning that functionally, there are no immediate changes.  The zswap
> mechanism will only come into effect once the backends have removed their
> shrink code.  The subsequent commits will address the modifications needed
> in the backends.
> 
> Link: https://lkml.kernel.org/r/20230612093815.133504-1-cerasuolodomenico@gmail.com
> Link: https://lkml.kernel.org/r/20230612093815.133504-2-cerasuolodomenico@gmail.com
> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
> Acked-by: Nhat Pham <nphamcs@gmail.com>
> Tested-by: Yosry Ahmed <yosryahmed@google.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
> Cc: Dan Streetman <ddstreet@ieee.org>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
> Cc: Seth Jennings <sjenning@redhat.com>
> Cc: Vitaly Wool <vitaly.wool@konsulko.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>