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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 26 Oct 2018 08:40:45 +0100 Received: from d06av24.portsmouth.uk.ibm.com (d06av24.portsmouth.uk.ibm.com [9.149.105.60]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w9Q7eif533226840 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 26 Oct 2018 07:40:44 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AB07242041; Fri, 26 Oct 2018 07:40:44 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4AAE942042; Fri, 26 Oct 2018 07:40:44 +0000 (GMT) Received: from localhost (unknown [9.79.235.97]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 26 Oct 2018 07:40:44 +0000 (GMT) Date: Fri, 26 Oct 2018 13:10:42 +0530 From: "Naveen N. Rao" Subject: Re: [PATCH v1 3/5] powerpc/pseries: Fix stolen time accounting when dtl debugfs is used To: Paul Mackerras References: <16929569199445cd09d9142505b2349620328b38.1540488386.git.naveen.n.rao@linux.vnet.ibm.com> <20181025210807.GA23232@blackberry> In-Reply-To: <20181025210807.GA23232@blackberry> User-Agent: astroid/0.14.0 (https://github.com/astroidmail/astroid) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 x-cbid: 18102607-0020-0000-0000-000002DA8842 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18102607-0021-0000-0000-00002129C001 Message-Id: <1540537881.qtnejr69k7.naveen@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2018-10-26_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1810260068 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, Jeremy Kerr , Steven Rostedt , Nathan Fontenot Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Paul Mackerras wrote: > On Fri, Oct 26, 2018 at 01:55:44AM +0530, Naveen N. Rao wrote: >> When the dtl debugfs interface is used, we usually set the >> dtl_enable_mask to 0x7 (DTL_LOG_ALL). When this happens, we start seeing >> DTL entries for all preempt reasons, including CEDE. In >> scan_dispatch_log(), we add up the times from all entries and account >> those towards stolen time. However, we should only be accounting stolen >> time when the preemption was due to HDEC at the end of our time slice. >=20 > It's always been the case that stolen time when idle has been > accounted as idle time, not stolen time. That's why we didn't check > for this in the past. >=20 > Do you have a test that shows different results (as in reported idle > and stolen times) with this patch compared to without? Ah ok, that makes sense now and explains why I couldn't observe much of=20 a difference in practice. However, I also went by the fact that there=20 are 7 other preemption reasons, which could impact our calculation. =20 Looking at the list again, it looks like H_CONFER/H_PROD and some faults=20 can also have an impact here, though they may be rare? Thanks, Naveen =