From: Roman Gushchin <guro@fb.com>
To: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.com>, Chris Down <chris@chrisdown.name>,
Andrew Morton <akpm@linux-foundation.org>,
<cgroups@vger.kernel.org>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 4/4] memcg: synchronously enforce memory.high for large overcharges
Date: Tue, 15 Feb 2022 15:27:32 -0800 [thread overview]
Message-ID: <Ygw25FypLsN9ZQaZ@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <20220211064917.2028469-5-shakeelb@google.com>
On Thu, Feb 10, 2022 at 10:49:17PM -0800, Shakeel Butt wrote:
> The high limit is used to throttle the workload without invoking the
> oom-killer. Recently we tried to use the high limit to right size our
> internal workloads. More specifically dynamically adjusting the limits
> of the workload without letting the workload get oom-killed. However due
> to the limitation of the implementation of high limit enforcement, we
> observed the mechanism fails for some real workloads.
>
> The high limit is enforced on return-to-userspace i.e. the kernel let
> the usage goes over the limit and when the execution returns to
> userspace, the high reclaim is triggered and the process can get
> throttled as well. However this mechanism fails for workloads which do
> large allocations in a single kernel entry e.g. applications that
> mlock() a large chunk of memory in a single syscall. Such applications
> bypass the high limit and can trigger the oom-killer.
>
> To make high limit enforcement more robust, this patch makes the limit
> enforcement synchronous only if the accumulated overcharge becomes
> larger than MEMCG_CHARGE_BATCH. So, most of the allocations would still
> be throttled on the return-to-userspace path but only the extreme
> allocations which accumulates large amount of overcharge without
> returning to the userspace will be throttled synchronously. The value
> MEMCG_CHARGE_BATCH is a bit arbitrary but most of other places in the
> memcg codebase uses this constant therefore for now uses the same one.
>
> Signed-off-by: Shakeel Butt <shakeelb@google.com>
> ---
> Changes since v1:
> - Based on Roman's comment simply the sync enforcement and only target
> the extreme cases.
Reviewed-by: Roman Gushchin <guro@fb.com>
This version indeed looks more safe to me.
Thanks!
prev parent reply other threads:[~2022-02-15 23:27 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-11 6:49 [PATCH v2 0/4] memcg: robust enforcement of memory.high Shakeel Butt
2022-02-11 6:49 ` [PATCH v2 1/4] memcg: refactor mem_cgroup_oom Shakeel Butt
2022-02-11 6:49 ` [PATCH v2 2/4] memcg: unify force charging conditions Shakeel Butt
2022-02-11 6:49 ` [PATCH v2 3/4] selftests: memcg: test high limit for single entry allocation Shakeel Butt
2022-02-15 23:28 ` Roman Gushchin
2022-02-11 6:49 ` [PATCH v2 4/4] memcg: synchronously enforce memory.high for large overcharges Shakeel Butt
2022-02-11 12:13 ` Chris Down
2022-02-11 20:36 ` Shakeel Butt
2022-02-16 13:12 ` Chris Down
2022-02-15 18:50 ` Shakeel Butt
2022-02-15 23:27 ` Roman Gushchin [this message]
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