From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C998F2580C8; Mon, 10 Feb 2025 16:20:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739204413; cv=none; b=Um1ZGfdAvhKAy2z5hiG8ZhtXhFXGnf106W9VJgq3zAbyw/1msOhvDCqZoXR+5xUjkyz2TcEI4OdWt1Oqd+Mj2yWYbmwUVVdbG2BZkq3G9MFsBvVvmJ2Xs/uLcbBOu/5XPSB+pvdxwwhObDHmPVEjsscxxy336tDNr/1o0UxtJNA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739204413; c=relaxed/simple; bh=PbUicCmIFdjpcUFcKr4bLsGE918h29ndeodZw27NPJY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gco3dtXASrCYporuADyoB11uDdySS2rvcZnssZP1qc3fsvChMNX5+1ermD+lyfeAFpRFYuvX5s38d0CKR9OJFBuk3JFSZh7vRtjwcLH1EHDmSdbgaWM5i9rwQAWJA8coQv4mpaw7K7As65IZlDqugjARYG9hZBzVl6TmWclbkZY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BpFPhpEh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BpFPhpEh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 244C4C4CED1; Mon, 10 Feb 2025 16:20:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739204413; bh=PbUicCmIFdjpcUFcKr4bLsGE918h29ndeodZw27NPJY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BpFPhpEh2J59IPGvPI1ojhA3QxLZfDTuh0//7bIMogtvZzlLGPhrtpOBiH4lcbFIb OPXAWvHq9AQJP2YyzVSSzP4z2GKw5TTEIyHpzzm4PL0b2qs1DU74P6Kku8p0LcBrDI S7Iw+MYQPBha48hvlxbl5bcEVSVfAJsT6mzZGaQ1tO89eNfk999NEuH9GKc6P3Hc85 iPm/3ctXUfMW5RJsWsorF4vbGYQlkIwguhlWSmrS4N7c9xdKsma7wPTd1BDoXuzDy4 K5805Z3XtHiR/dfYBRFasIuCepp06tYt5ybMzeMtmoeqqf9oQnC5DJ+lbHRK7wlH1v LYADDn1Cz2TNg== Date: Mon, 10 Feb 2025 06:20:12 -1000 From: Tejun Heo To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: Abel Wu , Johannes Weiner , Jonathan Corbet , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Thomas Gleixner , Yury Norov , Andrew Morton , Bitao Hu , Chen Ridong , "open list:CONTROL GROUP (CGROUP)" , "open list:DOCUMENTATION" , open list Subject: Re: [PATCH v2 3/3] cgroup/rstat: Add run_delay accounting for cgroups Message-ID: References: <20250125052521.19487-1-wuyun.abel@bytedance.com> <20250125052521.19487-4-wuyun.abel@bytedance.com> <3wqaz6jb74i2cdtvkv4isvhapiiqukyicuol76s66xwixlaz3c@qr6bva3wbxkx> <9515c474-366d-4692-91a7-a4c1a5fc18db@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Feb 10, 2025 at 04:38:56PM +0100, Michal Koutný wrote: ... > The challenge is with nr (assuming they're all runnable during Δt), that > would need to be sampled from /sys/kernel/debug/sched/debug. But then > you can get whatever load for individual cfs_rqs from there. Hm, does it > even make sense to add up run_delays from different CPUs? The difficulty in aggregating across CPUs is why some and full pressures are defined the way they are. Ideally, we'd want full distribution of stall states across CPUs but both aggregation and presentation become challenging, so some/full provide the two extremes. Sum of all cpu_delay adds more incomplete signal on top. I don't know how useful it'd be. At meta, we depend on PSI a lot when investigating resource problems and we've never felt the need for the sum time, so that's one data point with the caveat that usually our focus is on mem and io pressures where some and full pressure metrics usually seem to provide sufficient information. As the picture provided by some and full metrics is incomplete, I can imagine adding the sum being useful. That said, it'd help if Able can provide more concrete examples on it being useful. Another thing to consider is whether we should add this across resources monitored by PSI - cpu, mem and io. Thanks. -- tejun