Re: [PATCH RFC 00/28] Eliminate Dying Memory Cgroup

[Kairui Song <ryncsn@gmail.com>]

On Fri, Apr 18, 2025 at 5:45 AM Roman Gushchin <roman.gushchin@linux.dev> wrote:
>
> On Fri, Apr 18, 2025 at 02:22:12AM +0800, Kairui Song wrote:
> >
> > We currently have some workloads running with `nokmem` due to objcg
> > performance issues. I know there are efforts to improve them, but so
> > far it's still not painless to have. So I'm a bit worried about
> > this...
>
> Do you mind sharing more details here?
>
> Thanks!

Hi,

Sorry for the late response, I was busy with another series and other works.

It's not hard to observe such slow down, for example a simple redis
test can expose it:

Without nokmem:
redis-benchmark -h 127.0.0.1 -q -t set,get -n 80000 -c 1
SET: 16393.44 requests per second, p50=0.055 msec
GET: 16956.34 requests per second, p50=0.055 msec

With nokmem:
redis-benchmark -h 127.0.0.1 -q -t set,get -n 80000 -c 1
SET: 17263.70 requests per second, p50=0.055 msec
GET: 17410.23 requests per second, p50=0.055 msec

And I'm testing with latest kernel:
uname -a
Linux localhost 6.15.0-rc2+ #1594 SMP PREEMPT_DYNAMIC Sun Apr 27
15:13:27 CST 2025 x86_64 GNU/Linux

This is just an example. For redis, it can be a workaround by using
things like redis pipeline, but not all workloads can be adjusted
that flexibly.

And the slowdown could be amplified in some cases.