Messages in this thread | | | Date | Wed, 19 Feb 2020 11:31:39 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: memcontrol: asynchronous reclaim for memory.high |
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On Wed, 19 Feb 2020 19:37:31 +0100 Michal Hocko <mhocko@kernel.org> wrote:
> On Wed 19-02-20 13:12:19, Johannes Weiner wrote: > > We have received regression reports from users whose workloads moved > > into containers and subsequently encountered new latencies. For some > > users these were a nuisance, but for some it meant missing their SLA > > response times. We tracked those delays down to cgroup limits, which > > inject direct reclaim stalls into the workload where previously all > > reclaim was handled my kswapd. > > I am curious why is this unexpected when the high limit is explicitly > documented as a throttling mechanism.
Yes, this sounds like a feature-not-a-bug.
But what was the nature of these stalls? If they were "stuck in D state waiting for something" then that's throttling. If they were "unexpected bursts of in-kernel CPU activity" then I see a better case.
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