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 DE0AE34B19F; Tue, 28 Jul 2026 16:37:39 +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=1785256661; cv=none; b=d6QdIehX7f7gJ/fSTFPv7eTgxfWGYV1NWtPE0cNT4RjtVa1NfJv5r4VJENRzFVOuUQnQ7jCXq6FgKwIVLu3nxxK8CA3H9xPgrilCZPSV/Z6vbo0aZ3+HU+dmbaJlpgoB645QHwBDH/vxMji3YV3Ho/i0ia96+Li3ASoa53hkRC4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785256661; c=relaxed/simple; bh=ZwumHLdDD05eqeamyWaZK6REcQd7t/8018MxvOhS168=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=enTRF4rDvD378Suw1Vt1aF3W5bok40vBq5gDTK5asRR+gD4ggNqPhJ29Fxx0RQMeXFARRbioRQNgD9h8RFZEpTIwsGcLINYeNk/Mh7/ikA4NIyzBvSxZzCy9Q+XMC8zn2OAvrQ2VXBrY9Ti4scfphB0BpeWiEXnw+HSDcLW77Pc= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=hEnna7Ki; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="hEnna7Ki" 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 296C6169E; Tue, 28 Jul 2026 09:37:35 -0700 (PDT) Received: from [10.1.39.91] (unknown [10.1.39.91]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 93C223F763; Tue, 28 Jul 2026 09:37:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785256659; bh=ZwumHLdDD05eqeamyWaZK6REcQd7t/8018MxvOhS168=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=hEnna7Ki1eXf0o228QAPXujM0mc1cgjWxZmZqNglm5YQYG4MPzs5n4oj5ST5kM5N/ GPCvWSdFsN71+hnvwBFECU1x2Iik5w/H5bPu8wxm2C3OmCMFRWOqwqAAC7ucRbikCi v0a7uyrtLKQewbyzEBnZptOIxmyAWeyJjyc9vy9k= Message-ID: <0b9b9c3d-8ba0-4329-9504-b9d33c627649@arm.com> Date: Tue, 28 Jul 2026 17:37:34 +0100 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: [PATCH] sched/idle: Stop the tick when no cpuidle driver is available From: Christian Loehle To: Joseph Salisbury , "Rafael J. Wysocki (Intel)" Cc: rafael.j.wysocki@intel.com, Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , frederic@kernel.org, linux-pm@vger.kernel.org, LKML , regressions@lists.linux.dev References: <096b42fa-107f-450d-b3b1-03bcad3f1e04@oracle.com> <5f5cb821-92ae-4539-ae81-a43e33a7ded5@arm.com> <774c3a68-6a6b-4e2e-a347-03e36953b750@arm.com> Content-Language: en-US In-Reply-To: <774c3a68-6a6b-4e2e-a347-03e36953b750@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Commit f4c31b07b136 ("sched: idle: Consolidate the handling of two special cases") changed the no-cpuidle-driver path to use the previous tick wakeup heuristic. Oracle reported a substantial sysbench regression on small OCI VM shapes with no cpuidle driver available. Reverting the commit recovered the lost performance. Restore the previous tick handling for the no-driver case while retaining the heuristic for the single-state cpuidle case. Fixes: f4c31b07b136 ("sched: idle: Consolidate the handling of two special cases") Reported-by: Joseph Salisbury Closes: https://lore.kernel.org/all/096b42fa-107f-450d-b3b1-03bcad3f1e04@oracle.com/ Signed-off-by: Christian Loehle --- Here's the actual patch, I'd still be curious about why this happens here... kernel/sched/idle.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 052435f4d3e3..a814f9d5759f 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -194,7 +194,7 @@ static void cpuidle_idle_call(bool stop_tick) } if (cpuidle_not_available(drv, dev)) { - idle_call_stop_or_retain_tick(stop_tick); + tick_nohz_idle_stop_tick(); default_idle_call(); goto exit_idle; -- 2.34.1