Re: [PATCH 3/3] memcg: reduce size of memcg vmstats structures

Roman Gushchin
2022-09-07T23:27:41Z

On Wed, Sep 07, 2022 at 04:35:37AM +0000, Shakeel Butt wrote:
> The struct memcg_vmstats and struct memcg_vmstats_percpu contains two
> arrays each for events of size NR_VM_EVENT_ITEMS which can be as large
> as 110. However the memcg v1 only uses 4 of those while memcg v2 uses
> 15. The union of both is 17. On a 64 bit system, we are wasting
> approximately ((110 - 17) * 8 * 2) * (nr_cpus + 1) bytes which is
> significant on large machines.
>
> This patch reduces the size of the given structures by adding one
> indirection and only stores array of events which are actually used by
> the memcg code. With this patch, the size of memcg_vmstats has reduced
> from 2544 bytes to 1056 bytes while the size of memcg_vmstats_percpu has
> reduced from 2568 bytes to 1080 bytes.

This is pretty impressive!

Thank you, Shakeel!

Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
for the series.

Thanks!