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

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Message-ID: <5e603850-2cfc-4eb6-a5cc-da5282525b0d@cdn77.com>
Date: Wed, 15 Oct 2025 15:57:29 +0200
From: Daniel Sedlak <daniel.sedlak@...77.com>
To: Shakeel Butt <shakeel.butt@...ux.dev>
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 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)?
> 
> 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?

Thanks!
Daniel