Re: [PATCH v2 0/2] memcg: reading memcg stats more efficiently

[Roman Gushchin <roman.gushchin@linux.dev>]

JP Kobryn <inwardvessel@gmail.com> writes:

> On 10/15/25 1:46 PM, Shakeel Butt wrote:
>> Cc memcg maintainers.
>> On Wed, Oct 15, 2025 at 12:08:11PM -0700, JP Kobryn wrote:
>>> When reading cgroup memory.stat files there is significant kernel overhead
>>> in the formatting and encoding of numeric data into a string buffer. Beyond
>>> that, the given user mode program must decode this data and possibly
>>> perform filtering to obtain the desired stats. This process can be
>>> expensive for programs that periodically sample this data over a large
>>> enough fleet.
>>>
>>> As an alternative to reading memory.stat, introduce new kfuncs that allow
>>> fetching specific memcg stats from within cgroup iterator based bpf
>>> programs. This approach allows for numeric values to be transferred
>>> directly from the kernel to user mode via the mapped memory of the bpf
>>> program's elf data section. Reading stats this way effectively eliminates
>>> the numeric conversion work needed to be performed in both kernel and user
>>> mode. It also eliminates the need for filtering in a user mode program.
>>> i.e. where reading memory.stat returns all stats, this new approach allows
>>> returning only select stats.

It seems like I've most of these functions implemented as part of
bpfoom: https://lkml.org/lkml/2025/8/18/1403

So I definitely find them useful. Would be nice to merge our efforts.

Thanks!