From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 2356F2E62A8 for ; Thu, 12 Feb 2026 09:55:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770890136; cv=none; b=gP/u/OQqiAA0oMHTWGZ+IgSORVFResOqP42IQYn+mWyxOzKUkScavtm91FuWKq8R+3VhWZPI67rSWWR/mvHJNmDDqoa1lre6XTFrTeAEn/+Vl9SRSgK+vYg2edSdDebtRZt8Qx9TteUnUYBWcCit1GmLykSEjoQpuGVEH7P/8AE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770890136; c=relaxed/simple; bh=olh+y43Mvb6l0Mx002qlDUuX+z7dQQkuwqQHMhz1FW8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S1tbINtSIAh0ddfABw2AwBh1UVOHg/qMDgpryW7J/v7nIJX2PMbMxXtt3+dpZPp7WNA+zh+nc/yE9B0BX+NKobQc6iWM8hrDbQUMBDq53kDGrBRJttBS6NYj1yYGlDswShi6LXcs41nlNOiNTmg23dVxXJfG9GiDScXK9cUgUJw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AA1DD339; Thu, 12 Feb 2026 01:55:26 -0800 (PST) Received: from [10.57.11.22] (unknown [10.57.11.22]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EEA983F632; Thu, 12 Feb 2026 01:55:28 -0800 (PST) Message-ID: <80d26683-5560-470d-8713-0ce64743f9dd@arm.com> Date: Thu, 12 Feb 2026 09:55:27 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9] sched/fair: Filter false overloaded_group case for EAS To: Qais Yousef , Vincent Guittot Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, pierre.gondois@arm.com, kprateek.nayak@amd.com, hongyan.xia2@arm.com, luis.machado@arm.com References: <20260206095454.1520619-1-vincent.guittot@linaro.org> <20260211014839.urv4kyi2lmnvl3su@airbuntu> Content-Language: en-US From: Christian Loehle In-Reply-To: <20260211014839.urv4kyi2lmnvl3su@airbuntu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/11/26 01:48, Qais Yousef wrote: > On 02/06/26 10:54, Vincent Guittot wrote: >> With EAS, a group should be set overloaded if at least 1 CPU in the group >> is overutilized but it can happen that a CPU is fully utilized by tasks >> because of clamping the compute capacity of the CPU. In such case, the CPU >> is not overutilized and as a result should not be set overloaded as well. >> >> group_overloaded being a higher priority than group_misfit, such group can >> be selected as the busiest group instead of a group with a mistfit task >> and prevents load_balance to select the CPU with the misfit task to pull >> the latter on a fitting CPU. >> >> Signed-off-by: Vincent Guittot >> Tested-by: Pierre Gondois >> --- >> >> This patch was part of a larger patchset [1] but makes sense on its own and has >> not changed since v2 >> >> [1] https://lore.kernel.org/all/20251202181242.1536213-1-vincent.guittot@linaro.org/ > > I don't mind this. But I think with the original series misfit will be handled > better with push lb, and if it is made to handle overloaded case (which my > initial testing shows it is easily doable and I can't see clear bad impact > yet), I think we can retire overutilized altogether. > The EAS wakeup path (and therefore the push lb for that matter) is costly and workloads are sensitive to it, it's trivial to see with hackbench. Overutilized prevents that. Arguments about PELT inaccuracies during periods of unmet compute demand (and therefore entirely bogus EAS computation results) aside, I don't see how we a push lb could retire OU? If anything you're paying twice the price then for these scenarios? > [snip]