Re: [PATCH 0/7] zsmalloc: redesign object alloc API

[Yosry Ahmed <yosry@kernel.org>]

On Thu, Nov 05, 2026 at 01:47:30PM +0900, Sergey Senozhatsky wrote:
> Both zram and zswap already have per-entry structures that store zsmalloc
> handles, so allocating a separate handle_cachep object per stored page is
> redundant.  This series embeds struct zs_handle directly into zram and
> zswap entries and drops handle_cachep, saving 8 bytes and a slab
> alloc/free per stored object (2MB per 1GB of swapped out 4K pages).

I always hated that extra layer of indirection, thanks for doing this!

> 
> It also folds zs_malloc() and zs_obj_write() into zs_store() so we don't
> take pool->lock and look up object location again right after allocation.
> 
> A simple zram test on a 24-vCPU VM
> ==================================
> 165 fewer kernel instructions and 0.7-1.8% fewer kernel cycles per write;
> lz4 single writer +2.3% IOPS / -2.6% average latency;
> 24 writers +0.9-+1.0% IOPS; no regressions.
> Memory: 8 bytes less per stored page.
> 
> Sergey Senozhatsky (7):
>   zram: drop stale comment in write_incompressible_page()
>   zram: drop get_slot_handle() and set_slot_handle()
>   zsmalloc: switch handle type to struct zs_handle
>   zram: allocate zsmalloc object under slot lock
>   zsmalloc: embed struct zs_handle into zram and zswap entries
>   zsmalloc: fold zs_obj_write() into zs_store()
>   zsmalloc: constify struct zs_handle pointer in read-only functions
> 
>  Documentation/admin-guide/mm/slab.rst        |   2 +-
>  Documentation/core-api/memory-allocation.rst |   2 +-
>  Documentation/mm/zsmalloc.rst                |   8 +-
>  drivers/block/zram/Kconfig                   |   1 +
>  drivers/block/zram/zram_drv.c                | 130 +++++-------
>  drivers/block/zram/zram_drv.h                |  10 +-
>  include/linux/zsmalloc.h                     |  37 +++-
>  mm/Kconfig                                   |   3 +
>  mm/zsmalloc.c                                | 204 +++++++++++--------
>  mm/zswap.c                                   |  21 +-
>  10 files changed, 229 insertions(+), 189 deletions(-)
> 
> -- 
> 2.56.0.398.g882cbad275-goog
> 
>