linux-kernel - Re: [RFC 0/1] Try to add memory allocation info for cgroup oom kill

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Message-ID: <gxildlinmmimk7rd4olsz4rstsiapttbjbtbtzbekrmfxbvuhh@cmio2ckbyzxn>
Date: Thu, 21 Aug 2025 14:26:42 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Yueyang Pan <pyyjason@...il.com>, 
	Kent Overstreet <kent.overstreet@...ux.dev>, Usama Arif <usamaarif642@...il.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/1] Try to add memory allocation info for cgroup oom kill

On Thu, Aug 21, 2025 at 01:00:36PM -0700, Suren Baghdasaryan wrote:
> On Thu, Aug 21, 2025 at 12:53 PM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> >
> > On Thu, Aug 21, 2025 at 12:18:00PM -0700, Yueyang Pan wrote:
> > > On Thu, Aug 21, 2025 at 11:35:19AM -0700, Shakeel Butt wrote:
> > > > On Thu, Aug 14, 2025 at 10:11:56AM -0700, Yueyang Pan wrote:
> > > > > Right now in the oom_kill_process if the oom is because of the cgroup
> > > > > limit, we won't get memory allocation infomation. In some cases, we
> > > > > can have a large cgroup workload running which dominates the machine.
> > > > > The reason using cgroup is to leave some resource for system. When this
> > > > > cgroup is killed, we would also like to have some memory allocation
> > > > > information for the whole server as well. This is reason behind this
> > > > > mini change. Is it an acceptable thing to do? Will it be too much
> > > > > information for people? I am happy with any suggestions!
> > > >
> > > > For a single patch, it is better to have all the context in the patch
> > > > and there is no need for cover letter.
> > >
> > > Thanks for your suggestion Shakeel! I will change this in the next version.
> > >
> > > >
> > > > What exact information you want on the memcg oom that will be helpful
> > > > for the users in general? You mentioned memory allocation information,
> > > > can you please elaborate a bit more.
> > > >
> > >
> > > As in my reply to Suren, I was thinking the system-wide memory usage info
> > > provided by show_free_pages and memory allocation profiling info can help
> > > us debug cgoom by comparing them with historical data. What is your take on
> > > this?
> > >
> >
> > I am not really sure about show_free_areas(). More specifically how the
> > historical data diff will be useful for a memcg oom. If you have a
> > concrete example, please give one. For memory allocation profiling, is
> > it possible to filter for the given memcg? Do we save memcg information
> > in the memory allocation profiling?
> 
> No, memory allocation profiling is not cgroup-aware. It tracks
> allocations and their code locations but no other context.

Thanks for the info. Pan, will having memcg info along with allocation
profile help your use-case? (Though adding that might not be easy or
cheaper)