From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout.gmx.net (mout.gmx.net [212.227.17.20]) (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 36C503DC87B; Mon, 28 Sep 2026 13:00:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=212.227.17.20 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790600435; cv=none; b=Gyckz3sC/n7suP5oDX2Vi9ThxQdjJzMc2tLnQDxnkd9PSBsnEKpElZGDP6Vrpc28MuzsnVDOipueqEXSk1KoDBGZcXBHODsP+FPQog4I9ZmTP7biyEdVMep+WTe6YguVvoQGOyIyKbluL69qLJqpGkBwfXhUiyXwjkFkC+WrGVU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790600435; c=relaxed/simple; bh=0ji0m/7TpVUZJeEnAvLR1aKypQLulQY/QfB/5mfR66U=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; 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References:Content-Type:Content-Transfer-Encoding:MIME-Version:cc: content-transfer-encoding:content-type:date:from:message-id: mime-version:reply-to:subject:to; b=fcFd6Mcsvn0HotrW1JbzaJipB2uaZe1IfncghthKkkAAqy/4iE4R0IM0zJyRQsfu Hd58+/cjh5rSRgJ6TtvH8LkMPM6zuS+wtegxIyp/BeYso9QRXcApDJ8fproG40Jnc ZxXBxA4VwADA2B4KE0ssm30IMHaNAYNY6DMLU2/BaraKsls8HkmbUvaa1b8fwA4Rh 9t98xxRG1jtwvvAVSb5U0wpZ/vKm6pYv39gsCboXXYe52VN1dI9e/wbGiejg6++CH SU8Vx+mWboFGL08gS64IGbx9HNHyGq9NkVOTtOze6buW3Eo4+POti0tlLUFD463v0 B+D/QAQ8HE/kcQb0KA== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from client.hidden.invalid by mail.gmx.net (mrgmx105 [212.227.17.168]) with ESMTPSA (Nemesis) id 1MVN6t-1xKhCv2HoN-00LaQL; Mon, 28 Sep 2026 15:00:10 +0200 Message-ID: <4d4f5fdee4d1f462ba3490a6b3921006285e7fcc.camel@gmx.de> Subject: Re: [REGRESSION] [PATCH v3 7/7] sched/eevdf: Move to a single runqueue From: Mike Galbraith To: Chen Yu , kprateek.nayak@amd.com Cc: Aishwarya Rambhadran , Peter Zijlstra , mingo@kernel.org, longman@redhat.com, chenridong@huaweicloud.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jstultz@google.com, qyousef@layalina.io, Ryan Roberts , chen.yu@linux.dev Date: Mon, 28 Sep 2026 15:00:04 +0200 In-Reply-To: References: <20260605105513.354837583@infradead.org> <20260605124052.227463677@infradead.org> <128e93ca1424630546e39f9e9c1377f8185f7644.camel@gmx.de> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Provags-ID: V03:K1:KUUPpKNXiKaXxpr5TCfYnbGZgGReCwKZl8TJDsOn10FYsPmYo2E 8avXXY8zGppimPpHwpm1Rlh8iig+/oaLZJENSS6MOjoLceMhKKz2YfWHQTphT9NyeuFxojf 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improvement on my machine, iff the memory bandwidth is saturated. B= y comparison, > if the memory bandwidth is low, stacking the wakee on top of the waker ca= uses harm. Ditto CPU wise. The impact of even modest waker/wakee concurrency is considerable. For much of netperf, the post-wakeup tail becomes a CPU service latency injection for the wakee when unnecessarily stacked.=20 While cache misses sting, those hurt. As box approaches saturation, stacking of somewhat synchronous stuff becomes a better bet. Aiming for having only waker's tail between wakee and CPU has decent chance of being a winner in a box full of wider obstacles. -Mike