Re: [PATCH v2] proc: add percpu populated pages count to meminfo

On Tue, Aug 07, 2018 at 11:47:23AM -0700, Dennis Zhou wrote:

From: "Dennis Zhou (Facebook)" <redacted>

Currently, percpu memory only exposes allocation and utilization
information via debugfs. This more or less is only really useful for
understanding the fragmentation and allocation information at a
per-chunk level with a few global counters. This is also gated behind a
config. BPF and cgroup, for example, have seen an increase use causing
increased use of percpu memory. Let's make it easier for someone to
identify how much memory is being used.

This patch adds the "Percpu" stat to meminfo to more easily look up how
much percpu memory is in use. This number includes the cost for all
allocated backing pages and not just isnight at the a unit, per chunk
level. Metadata is excluded. I think excluding metadata is fair because
the backing memory scales with the numbere of cpus and can quickly
outweigh the metadata. It also makes this calculation light.

Signed-off-by: Dennis Zhou <redacted>

Acked-by: Roman Gushchin <redacted>

It's super useful! I've seen hosts in production which have
tens and hundreds on megabytes in per-cpu memory, and with
vmalloc counters being defined to 0, it's really hard
to notice and track down.

Thanks, Dennis!