Re: [PATCH v4 1/1] mm: vmscan: Reduce throttling due to a failure to make progress'

Mel Gorman
2022-02-23T12:50:13Z

On Tue, Feb 22, 2022 at 12:27:31PM -0500, Shuang Zhai wrote:
> Mel Gorman wrote:
> > On Mon, Feb 14, 2022 at 04:10:50PM -0500, Shuang Zhai wrote:
> > > Hi Mel,
> > >
> > > Mel Gorman wrote:
> > > >
> > > > Mike Galbraith, Alexey Avramov and Darrick Wong all reported similar
> > > > problems due to reclaim throttling for excessive lengths of time.
> > > > In Alexey's case, a memory hog that should go OOM quickly stalls for
> > > > several minutes before stalling. In Mike and Darrick's cases, a small
> > > > memcg environment stalled excessively even though the system had enough
> > > > memory overall.
> > > >
> > >
> > > I recently found a regression when I tested MGLRU with fio on Linux
> > > 5.16-rc6 [1]. After this patch was applied, I re-ran the test with Linux
> > > 5.16, but the regression has not been fixed yet.
> > >
> >
> > Am I correct in thinging that this only happens with MGLRU?
>
> Sorry about the confusion and let me clarify on this. The regression happens
> on upstream Linux with the default page replacement mechanism.

Ok, the fio command for me simply exits with an error and even if it didn't
the test machine I have with persistent memory does not have enough pmem
to trigger memory reclaim issues with fio. Can you do the following please?

# echo 1 > vmscan/mm_vmscan_throttled/enable
# cat /sys/kernel/debug/tracing/trace_pipe > trace.out

and run the test? Compress trace.out with xz and send it to me by mail.
If the trace is too large, send as much as you can.

--
Mel Gorman
SUSE Labs