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From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Shakeel Butt" <shakeel.butt@linux.dev>,
	"Johannes Weiner" <hannes@cmpxchg.org>,
	"Michal Koutný" <mkoutny@suse.com>,
	"Michal Hocko" <mhocko@kernel.org>,
	"Roman Gushchin" <roman.gushchin@linux.dev>,
	"Muchun Song" <muchun.song@linux.dev>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Juri Lelli" <juri.lelli@redhat.com>,
	"Vincent Guittot" <vincent.guittot@linaro.org>,
	"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
	"Valentin Schneider" <vschneid@redhat.com>,
	"K Prateek Nayak" <kprateek.nayak@amd.com>,
	"Suren Baghdasaryan" <surenb@google.com>,
	"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
	"David Dai" <david.dai@linux.dev>,
	"JP Kobryn" <jp.kobryn@linux.dev>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Aaron Lu" <ziqianlu@bytedance.com>,
	"Daniel Jordan" <daniel.m.jordan@oracle.com>,
	"Hao Lee" <haolee.swjtu@gmail.com>,
	kernel-team@meta.com, cgroups@vger.kernel.org,
	bpf@vger.kernel.org, linux-mm@kvack.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/7] cgroup: charge kernel work to the cgroup it is done for
Date: Thu, 01 Oct 2026 08:59:36 -1000	[thread overview]
Message-ID: <4a8e64483eae4a8b7524650c7d54453f@kernel.org> (raw)
In-Reply-To: <20261001105909.GL4121339@noisy.programming.kicks-ass.net>

Hello, Peter.

On Thu, Oct 01, 2026 at 12:59:09PM +0200, Peter Zijlstra wrote:
> Ideally RX would be split for each network queue, rather than lumped
> into the one giant softirq that nobody owns.

Rx can be split per queue but the granularity doesn't match. There can be
way more cgroups than the hardware can split queues for.

> Furthermore, without ingress throttling, your RX back charge could
> completely deplete the actual cgroup time quota.

If rx processing slows down, the rx traffic slows down with it. We'd
likely still want to allot some minimum amount of time to non-rx work
while making sure the debt doesn't spiral out of control. If a dedicated
kthread were handling rx for the cgroup, rx would be sharing CPU time with
the rest of the cgroup without choking it completely. The back charging
can follow the same corollary.

> Anyway, if you get per queue RX processing threads, then you can move
> them into cgroups where so desired.

Same limit here. There are setups with a lot more cgroups than CPUs.

Thanks.

--
tejun

  parent reply	other threads:[~2026-10-01 18:59 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-24 18:47 Shakeel Butt
2026-09-24 18:47 ` [RFC PATCH 1/7] cgroup: add cgroup_account_system_time() Shakeel Butt
2026-09-24 18:47 ` [RFC PATCH 2/7] cgroup: add set_active_cgroup() to charge CPU time to a cgroup Shakeel Butt
2026-09-24 18:47 ` [RFC PATCH 3/7] psi: charge pressure to the task's active cgroup Shakeel Butt
2026-09-24 18:47 ` [RFC PATCH 4/7] sched/fair: add cfs_bandwidth_charge() for kernel work done for a cgroup Shakeel Butt
2026-09-24 18:47 ` [RFC PATCH 5/7] cgroup: take set_active_cgroup() time out of the cgroup's cpu.max Shakeel Butt
2026-09-24 18:47 ` [RFC PATCH 6/7] memcg: charge high_work reclaim to the memcg Shakeel Butt
2026-09-24 18:47 ` [RFC PATCH 7/7] selftests: cgroup: check that high_work reclaim is charged " Shakeel Butt
2026-09-24 20:28 ` [RFC PATCH 0/7] cgroup: charge kernel work to the cgroup it is done for Tejun Heo
2026-09-24 21:11   ` Shakeel Butt
2026-09-28 22:39     ` Tejun Heo
2026-10-01 10:59   ` Peter Zijlstra
2026-10-01 12:18     ` Peter Zijlstra
2026-10-01 16:00       ` Shakeel Butt
2026-10-01 12:40     ` Sebastian Andrzej Siewior
2026-10-01 18:59     ` Tejun Heo [this message]
2026-10-01 10:54 ` Peter Zijlstra
  -- strict thread matches above, loose matches on Subject: below --
2026-09-24 18:45 Shakeel Butt
2026-09-24 18:50 ` Shakeel Butt

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