Re: [PATCH v6 13/19] mm: memcg/slab: simplify memcg cache creation

Shakeel Butt
2020-06-22T17:29:45Z

On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@fb.com> wrote:
>
> Because the number of non-root kmem_caches doesn't depend on the
> number of memory cgroups anymore and is generally not very big,
> there is no more need for a dedicated workqueue.
>
> Also, as there is no more need to pass any arguments to the
> memcg_create_kmem_cache() except the root kmem_cache, it's
> possible to just embed the work structure into the kmem_cache
> and avoid the dynamic allocation of the work structure.
>
> This will also simplify the synchronization: for each root kmem_cache
> there is only one work. So there will be no more concurrent attempts
> to create a non-root kmem_cache for a root kmem_cache: the second and
> all following attempts to queue the work will fail.
>
>
> On the kmem_cache destruction path there is no more need to call the
> expensive flush_workqueue() and wait for all pending works to be
> finished. Instead, cancel_work_sync() can be used to cancel/wait for
> only one work.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

Why not pre-allocate the non-root kmem_cache at the kmem_cache
creation time? No need for work_struct, queue_work() or
cancel_work_sync() at all.