From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 CB5B71E9B0F for ; Mon, 20 Jan 2025 15:50:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737388247; cv=none; b=SkzKDdCkev7lXfL6/+XUdmZd9+T2JrHdzAIGzPx6+0gnD7b8VMCbXHt6MLeZ19U6jgSUEsL/SE4R/dglNVdO2q/eEl96N9kYRvOpzOe2VVps6uLJGnDOAImh1+X1OtpAmqyV0Ip7ToGMdmhxDz+KOkBnztX8gTsLPFaGSVaXrTk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737388247; c=relaxed/simple; bh=t1WUxRy4eGnpes0GZimQAD8XyfAQn+Z3KwMgxXq72QU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Z0NeY/Ac+AiUB8yMahM/YnnPhZ0pJHgMmQLkRjXBq4UyTl+i1B+CKySNI5/C+cQLH8pLf0lrwFq2+aWavRDwwK88bNYV7KidvchmibtPX1m4J+T8MmaL1SvAJnRgBpGP8s1jUMHBr5qAekv1PVjxX4vhx2sCVo8QTttqNabSu+w= 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=hp67LqiD; arc=none smtp.client-ip=170.10.133.124 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="hp67LqiD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1737388243; 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=tMAkoPEbp1X/1fbqmcjUBuRkyr/p8lqtKYU91SycHTM=; b=hp67LqiDtfMtLN8SjHC3qIXTq5IdNWW4boj6LHH/NoR0CIvHDJsSGtUNm80S00QZ1GeRzQ m+qImPDeO4m6BsPXjBX7GFuVG8FtzTjcjNWzYUkPJoxmQ3aVOi3NJuOch0t0A78AVxi8Cw jW3sS1aqJCftzSXFkxsw+i1cYRaRjQM= Received: from mx-prod-mc-03.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-668-4zMjq5AaN9eRpyYE_hzzbQ-1; Mon, 20 Jan 2025 10:50:41 -0500 X-MC-Unique: 4zMjq5AaN9eRpyYE_hzzbQ-1 X-Mimecast-MFC-AGG-ID: 4zMjq5AaN9eRpyYE_hzzbQ Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BB80E1956062; Mon, 20 Jan 2025 15:50:39 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.104]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 48A181956094; Mon, 20 Jan 2025 15:50:35 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 20 Jan 2025 16:50:14 +0100 (CET) Date: Mon, 20 Jan 2025 16:50:10 +0100 From: Oleg Nesterov To: kernel test robot Cc: oe-lkp@lists.linux.dev, lkp@intel.com, Christian Brauner , WangYuli , linux-fsdevel@vger.kernel.org, Mateusz Guzik Subject: Re: [linux-next:master] [pipe_read] aaec5a95d5: stress-ng.poll.ops_per_sec 11.1% regression Message-ID: <20250120155009.GD7432@redhat.com> References: <202501201311.6d25a0b9-lkp@intel.com> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <202501201311.6d25a0b9-lkp@intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Again, I'll try to take another look tomorrow. Not sure I will find the explanation though... But can you help? I know nothing about stress-ng. Google finds a lot of stress-ng repositories, I've clone the 1st one https://github.com/ColinIanKing/stress-ng/blob/master/stress-poll.c hopefully this is what you used. On 01/20, kernel test robot wrote: > > 9.45 -6.3 3.13 ± 9% perf-profile.calltrace.cycles-pp.pipe_read.vfs_read.ksys_read.do_syscall_64.entry_SYSCALL_64_after_hwframe > ... > 10.00 -6.5 3.53 ± 9% perf-profile.children.cycles-pp.pipe_read > 2.34 -1.3 1.07 ± 9% perf-profile.children.cycles-pp.pipe_poll Could you explain what do these numbers mean and how there are calculated? "git-grep cycles-pp" find nothing in stress-ng/ and tools/perf/ > kernel test robot noticed a 11.1% regression of stress-ng.poll.ops_per_sec on: same for ops_per_sec > 6150 -47.8% 3208 stress-ng.time.percent_of_cpu_this_job_got same for percent_of_cpu_this_job_got > 2993 -50.6% 1477 stress-ng.time.system_time > 711.20 -36.0% 454.85 stress-ng.time.user_time Is that what I think it is?? Does it run faster? Or it exits after some timeout and the decrease in system/user_time can be explained by the change in the mysterious 'percent_of_cpu_this_job_got' above? Oleg.