Re: [PATCH] mm/slub: improve count_partial() for CONFIG_SLUB_CPU_PARTIAL

[Christopher Lameter]

On Thu, 27 Feb 2020, Roman Gushchin wrote:

> 1) Reading /proc/slabinfo can cause latency spikes in concurrent memory allocations.
>    This is the problem which Wen raised initially.

Ok. Maybe cache the values or do not read /proc/slabinfo? Use
/sys/kernel/slab/... instead?

> 2) The number of active objects as displayed in /proc/slabinfo is misleadingly
>    big if CONFIG_SLUB_CPU_PARTIAL is set.

Ok that cou.d be fixed by counting the partial slabs when computing
/proc/slabinfo output but that would increase the times even more.

> Maybe mixing them in a single workaround wasn't the best idea, but what do you
> suggest instead?

Read select values from /sys/kernel/slab/.... to determine the values you
need and avoid reading those that cause latency spikes. Use the number of
slabs for example to estimate the number of objects instead of the number
of objects which requires scanning through all the individual slab pages.