Re: [RFC PATCH] zsmalloc: make common caches global

[Sergey Senozhatsky]

On (26/01/19 13:43), Nhat Pham wrote:
> On Thu, Jan 15, 2026 at 8:49 PM Sergey Senozhatsky
> <senozhatsky@xxxxxxxxxxxx> wrote:
> >
> > Currently, zsmalloc creates kmem_cache of handles and zspages
> > for each pool, which may be suboptimal from the memory usage
> > point of view (extra internal fragmentation per pool).  Systems
> > that create multiple zsmalloc pools may benefit from shared
> > common zsmalloc caches.
> >
> > Make handles and zspages kmem caches global.
> 
> Hmm yeah this sounds reasonable to me. No reason to have dedicated
> kmem_cache per zs_pool (in the case of zswap, I suppose it's one for
> each compression algorithm, which is usually just one - but still...).
> 
> Is there any lock contention implications?

cache_alloc_handle()/cache_alloc_zspage() (and their free counterparts)
are called outside of scope of any zsmalloc locks, so the upper boundary
on the number of concurrent callers is the same - num_online_cpus().