Re: [PATCH v6 12/19] mm: memcg/slab: use a single set of kmem_caches for all accounted allocations

[Shakeel Butt]

On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@xxxxxx> wrote:
>
> This is fairly big but mostly red patch, which makes all accounted
> slab allocations use a single set of kmem_caches instead of
> creating a separate set for each memory cgroup.
>
> Because the number of non-root kmem_caches is now capped by the number
> of root kmem_caches, there is no need to shrink or destroy them
> prematurely. They can be perfectly destroyed together with their
> root counterparts. This allows to dramatically simplify the
> management of non-root kmem_caches and delete a ton of code.
>
> This patch performs the following changes:
> 1) introduces memcg_params.memcg_cache pointer to represent the
>    kmem_cache which will be used for all non-root allocations
> 2) reuses the existing memcg kmem_cache creation mechanism
>    to create memcg kmem_cache on the first allocation attempt
> 3) memcg kmem_caches are named <kmemcache_name>-memcg,
>    e.g. dentry-memcg
> 4) simplifies memcg_kmem_get_cache() to just return memcg kmem_cache
>    or schedule it's creation and return the root cache
> 5) removes almost all non-root kmem_cache management code
>    (separate refcounter, reparenting, shrinking, etc)
> 6) makes slab debugfs to display root_mem_cgroup css id and never
>    show :dead and :deact flags in the memcg_slabinfo attribute.
>
> Following patches in the series will simplify the kmem_cache creation.
>
> Signed-off-by: Roman Gushchin <guro@xxxxxx>
> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>

This is a very satisfying patch.

Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>