Re: [PATCH v2] mm/zsmalloc: simplify shrinker init/destroy

[Michal Hocko <mhocko@kernel.org>]

On Wed 20-12-17 00:25:36, Sergey Senozhatsky wrote:
> Hi Michal,
> 
> On (12/19/17 16:13), Michal Hocko wrote:
> > On Tue 19-12-17 13:49:12, Aliaksei Karaliou wrote:
> > [...]
> > > @@ -2428,8 +2422,8 @@ struct zs_pool *zs_create_pool(const char *name)
> > >  	 * Not critical, we still can use the pool
> > >  	 * and user can trigger compaction manually.
> > >  	 */
> > > -	if (zs_register_shrinker(pool) == 0)
> > > -		pool->shrinker_enabled = true;
> > > +	(void) zs_register_shrinker(pool);
> > > +
> > >  	return pool;
> > 
> > So what will happen if the pool is alive and used without any shrinker?
> > How do objects get freed?
> 
> we use shrinker for "optional" de-fragmentation of zsmalloc pools. we
> don't free any objects from that path. just move them around within their
> size classes - to consolidate objects and to, may be, free unused pages
> [but we first need to make them "unused"]. it's not a mandatory thing for
> zsmalloc, we are just trying to be nice.

OK, it smells like an abuse of the API but please add a comment
clarifying that.

Thanks!
-- 
Michal Hocko
SUSE Labs

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