From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 3263C20125C for ; Wed, 13 Nov 2024 18:19:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731521982; cv=none; b=pKnD9jhz9SCAL0y8WrzST8BjS+LG5tMv+F5XPD00jeJ1XUmg2K91lEu56rTPYLQgmlMjW5NS4qwuhrFVl02vuEriYUwEZuNv0T5LqukcdAP+kmpjF1T9rQPocXJP/YIwMXl/qtbmB3z2UvmjITbZhrZLybqXNn2vliF5doY7GAk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731521982; c=relaxed/simple; bh=he7PZ11vgkkKFwqChZr6a3LHZsCGCrxCQFWeyDR2zM0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JIxbhfn4lLGCf5/6zCPknROZBcteBbklygxVz1nyhRbW28qlXN9rz+csWnrPaw7KEev9Uuf0OPKotrF/MXgSW+rdImJjP9nmTYqJDAKo5rlmL3UZQh0C5V7VTDdzsc01jg/41NljX6KaTzueskPtntI8gj35y0ekgnX7yqL0n0U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ECDy28lY; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ECDy28lY" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1731521980; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/XStPcwU28nRliHCrzV+elVqEzbDdwWRfdYSMPsom20=; b=ECDy28lYu8ytEoK2WhZHDrS6U4/kXabf4Ec3UMAJYsKSbkMIR1iEYX3aE2FkinYJGuTkxr 89BbHTj5QlsFUC/BKx+QF685umooouLnhpt03AJ7h18LDVx/wFYDdftrfhbb2EWlV2HPP6 wdmgEOqiXsz0aB4hDfHIVz51twxij9k= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-279-PBDdrrqZN1uNHPUkgNlkFA-1; Wed, 13 Nov 2024 13:19:38 -0500 X-MC-Unique: PBDdrrqZN1uNHPUkgNlkFA-1 X-Mimecast-MFC-AGG-ID: PBDdrrqZN1uNHPUkgNlkFA Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D91171955EE8; Wed, 13 Nov 2024 18:19:36 +0000 (UTC) Received: from pauld.westford.csb (unknown [10.22.80.158]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5883019560A3; Wed, 13 Nov 2024 18:19:33 +0000 (UTC) Date: Wed, 13 Nov 2024 13:19:30 -0500 From: Phil Auld To: Joseph Salisbury Cc: peterz@infradead.org, mingo@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, Steven Rostedt , bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [REGRESSION] sched/fair: Add lag based placement Message-ID: <20241113181930.GD402105@pauld.westford.csb> References: <58289b1c-8a56-4607-8632-d36aef1fc5dd@oracle.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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <58289b1c-8a56-4607-8632-d36aef1fc5dd@oracle.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Hi, On Wed, Nov 13, 2024 at 01:03:00PM -0500 Joseph Salisbury wrote: > Hello, > > During performance testing, we found a regression of ~9% performance with > the TPCC benchmark.   This performance regression was introduced in > v6.6-rc1.  After a bisect, the following commit was identified as the cause > of the regression: > > 86bfbb7ce4f6 ("sched/fair: Add lag based placement") > > I was hoping to get some feedback from the scheduler folks.  Do you think > gathering any additional data will help diagnose this issue?  Are there any > tunable options that can changed to see how performance is affected? > You can try turning off the PLACE_LAG sched feature: echo NO_PLACE_LAG > /sys/kernel/debug/sched/features It's not what I'd call a tunable but it would allow you to test w/o it and see what it does. It should allow you to switch back and forth easily for testing. Cheers, Phil > > Thanks, > > Joe > > > > > > > > --