Re: [PATCH v3 17/19] mm: memcg/slab: use a single set of kmem_caches for all allocations

From: Vlastimil Babka
Date: Tue May 26 2020 - 10:55:09 EST

On 4/22/20 10:47 PM, Roman Gushchin wrote:
> Instead of having two sets of kmem_caches: one for system-wide and
> non-accounted allocations and the second one shared by all accounted
> allocations, we can use just one.
> The idea is simple: space for obj_cgroup metadata can be allocated
> on demand and filled only for accounted allocations.
> It allows to remove a bunch of code which is required to handle
> kmem_cache clones for accounted allocations. There is no more need
> to create them, accumulate statistics, propagate attributes, etc.
> It's a quite significant simplification.
> Also, because the total number of slab_caches is reduced almost twice
> (not all kmem_caches have a memcg clone), some additional memory
> savings are expected. On my devvm it additionally saves about 3.5%
> of slab memory.
> Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Signed-off-by: Roman Gushchin <guro@xxxxxx>

Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>

However, as this series will affect slab fastpaths, and perhaps especially this
patch will affect even non-kmemcg allocations being freed, I'm CCing Jesper and
Mel for awareness as they AFAIK did work on network stack memory management
performance, and perhaps some benchmarks are in order...