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imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=OqmkmC+B; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of tj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=tj@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790881178; b=oACGU1JW69W1wPhgEVrJCdtmgD99TSeM3M6T30f4J6JrgnpgBlud0DDbfwVQTviCIpLNrx gkshe1/sP9fuDygnTMXzvb4pUY1cyG+r9yGE5nwqDJk1YIgoshPMby1TTNhT+50COKWs2f UDP1dpA4vTO8nEH3/bQIZVmfByb7nfk= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 949C64094F; Thu, 1 Oct 2026 18:59:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 547CB1F000FF; Thu, 1 Oct 2026 18:59:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790881177; bh=dbqpPhdVg+JjB04z8Xrp7o2CiVP31iN8OSuqPExIta4=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=OqmkmC+Ba6BnMRAC8P/rjHkzAwaaowPo5wlSsyTYeNoXx77Gdgz1fAznYvNzNJCr3 fdxcp+352A26HkH9iW5RwIUvEzNH555zBtM5tkW35ULQWFKqz+nfvl6Pg+7QUocZbz IXz1Hv+KmDuEgeLFHh39ze2SZ9daSCUthTAEWRbGTYjIvHaxYPhylfXkXu5bs+eT4W Rrub4xGtfhMMTgb4RbUi5JnmTEQKpY+U2pOXEdne0addK0xQVq6NpQ8ErLdOzmSFKj tnP2H8TKpVMuCDOltGWIZFWu4/pPc6PtFUhr4hTAAZCCKC5UxR8mRkn64waBdzs7r8 DF4bfCPwjmANw== Date: Thu, 01 Oct 2026 08:59:36 -1000 Message-ID: <4a8e64483eae4a8b7524650c7d54453f@kernel.org> From: Tejun Heo To: Peter Zijlstra Cc: Shakeel Butt , Johannes Weiner , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Michal Hocko , Roman Gushchin , Muchun Song , Andrew Morton , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Suren Baghdasaryan , Kumar Kartikeya Dwivedi , David Dai , JP Kobryn , Frederic Weisbecker , Aaron Lu , Daniel Jordan , Hao Lee , 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 In-Reply-To: <20261001105909.GL4121339@noisy.programming.kicks-ass.net> References: <20260924184714.912181-1-shakeel.butt@linux.dev> <20261001105909.GL4121339@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: 8arf8mnic4hwznbm5mqws4ncmtsz1q7s X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A4B33180004 X-HE-Tag: 1790881178-100738 X-HE-Meta: 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 Xgf/JMSF m3eDcQTEKmDSrfFLj7dcEsGoFx0l1AG/NRBtMaPdVxhUORIr8BEKD7G851Q2C7ZR0lhvq9nBWnxArWY+CG22q1kqlK750btY6UYl1m78IgOS3rEsKOly/wacq5uIrQBoaLSQRliTnRBqt9Y/mTg5KGhTKy/x+xtAjrzJR/UkOZ6XO1/G7yc2T1L2dKS/ZeX2LZfe0CuDj4ECI8Ap8tw4pTfyz+Yh5D7+AbREwctpc0fIwWAMDmo+LAfV2HmHfXcOnJKiIbty6+8KTEG1hOf/hIw3kPKLfQaE36eMpt4kWhQ2TC48ZXUPwsP2xZLHDrW7sngLVtBpDdXDRLBNCCKWjqv/lwZ7yIUcB7T5s9lDnYVRmw7Q= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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