netdev - Re: [PATCH v5] memcg: expose socket memory pressure in a cgroup

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Message-ID: <xfvvlbicyui22lhwptmdxtjfmcyei3m2bhhie7l2vjw4xa23cf@lhuh5q7vhwt4>
Date: Wed, 15 Oct 2025 11:36:01 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Daniel Sedlak <daniel.sedlak@...77.com>
Cc: Roman Gushchin <roman.gushchin@...ux.dev>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Jonathan Corbet <corbet@....net>, Neal Cardwell <ncardwell@...gle.com>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, David Ahern <dsahern@...nel.org>, 
	Andrew Morton <akpm@...ux-foundation.org>, Yosry Ahmed <yosry.ahmed@...ux.dev>, linux-mm@...ck.org, 
	netdev@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>, 
	Michal Hocko <mhocko@...nel.org>, Muchun Song <muchun.song@...ux.dev>, cgroups@...r.kernel.org, 
	Tejun Heo <tj@...nel.org>, Michal Koutný <mkoutny@...e.com>, 
	Matyas Hurtik <matyas.hurtik@...77.com>
Subject: Re: [PATCH v5] memcg: expose socket memory pressure in a cgroup

On Wed, Oct 15, 2025 at 03:57:29PM +0200, Daniel Sedlak wrote:
> On 10/14/25 10:32 PM, Shakeel Butt wrote:
> > On Mon, Oct 13, 2025 at 04:30:53PM +0200, Daniel Sedlak wrote:
> > [...]
> > > > > > > How about we track the actions taken by the callers of
> > > > > > > mem_cgroup_sk_under_memory_pressure()? Basically if network stack
> > > > > > > reduces the buffer size or whatever the other actions it may take when
> > > > > > > mem_cgroup_sk_under_memory_pressure() returns, tracking those actions
> > > > > > > is what I think is needed here, at least for the debugging use-case.
> > > 
> > > I am not against it, but I feel that conveying those tracked actions (or how
> > > to represent them) to the user will be much harder. Are there already
> > > existing APIs to push this information to the user?
> > > 
> > 
> > I discussed with Wei Wang and she suggested we should start tracking the
> > calls to tcp_adjust_rcv_ssthresh() first. So, something like the
> > following. I would like feedback frm networking folks as well:
> 
> Looks like a good start. Are you planning on sending this patch separately,
> or can we include it in our v6 (with maybe slight modifications)?

What else you are planning to add in v6?

> > 
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 873e510d6f8d..5fe254813123 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -52,6 +52,7 @@ enum memcg_memory_event {
> >   	MEMCG_SWAP_HIGH,
> >   	MEMCG_SWAP_MAX,
> >   	MEMCG_SWAP_FAIL,
> > +	MEMCG_SOCK_THROTTLED,
> 
> This probably should be MEMCG_TCP_SOCK_THROTTLED, because it checks only
> tcp_under_memory_pressure, however there is also the
> sk_under_memory_pressure used in net/sctp/sm_statefuns.c:6597 to also reduce
> the sending rate. Or also add the counter there and keep the name?

Yeah makes sense to add the counter in sctp as well.