From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68129C43331 for ; Fri, 6 Sep 2019 13:56:05 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AF5B9206B8 for ; Fri, 6 Sep 2019 13:56:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AF5B9206B8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46Pzc04CLMzDqBg for ; Fri, 6 Sep 2019 23:56:00 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=srikar@linux.vnet.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46PzTK2z0pzDqPj for ; Fri, 6 Sep 2019 23:50:12 +1000 (AEST) Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x86DlNt8124938 for ; Fri, 6 Sep 2019 09:50:07 -0400 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0b-001b2d01.pphosted.com with ESMTP id 2uuns4xtub-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 06 Sep 2019 09:50:07 -0400 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 6 Sep 2019 14:50:02 +0100 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x86Do16359047942 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 6 Sep 2019 13:50:01 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C7AF9A4055; Fri, 6 Sep 2019 13:50:01 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 99EC7A404D; Fri, 6 Sep 2019 13:50:00 +0000 (GMT) Received: from linux.vnet.ibm.com (unknown [9.126.150.29]) by d06av23.portsmouth.uk.ibm.com (Postfix) with SMTP; Fri, 6 Sep 2019 13:50:00 +0000 (GMT) Date: Fri, 6 Sep 2019 19:19:59 +0530 From: Srikar Dronamraju To: Nathan Lynch Subject: Re: [PATCH v2 3/4] powerpc/numa: Early request for home node associativity References: <20190829055023.6171-1-srikar@linux.vnet.ibm.com> <20190829055023.6171-4-srikar@linux.vnet.ibm.com> <87tv9qqzm7.fsf@linux.ibm.com> <20190906034110.GA12412@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20190906034110.GA12412@linux.vnet.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-TM-AS-GCONF: 00 x-cbid: 19090613-0028-0000-0000-00000398843F X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19090613-0029-0000-0000-0000245ADDCC Message-Id: <20190906134959.GB12412@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-09-06_06:, , 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=8.0.1-1906280000 definitions=main-1909060147 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: , Reply-To: Srikar Dronamraju Cc: Satheesh Rajendran , linuxppc-dev , Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" > > Regardless, I have an annoying question :-) Isn't it possible that, > > while Linux is calling vphn_get_nid() for each logical cpu in sequence, > > the platform could change a virtual processor's node assignment, > > potentially causing sibling threads to get different node assignments > > and producing an incoherent topology (which then leads to sched domain > > assertions etc)? > > > > Right, its certainly possible for node assignment to change while we iterate > through the siblings. Do you have an recommendations? > One thingk that I forgot to add was we already cache the cpu_to_node mapping. If the mapping is around, we still don't lookup the nid. However its still possible that in the first iteration where we cache the nid's. we still end up with different nids for different siblings if node associativity changes in between. > > If so, I think more care is needed. The algorithm should make the vphn > > call only once per cpu node, I think? > > I didn't get "once per cpu node", How do we know which all cpus are part of > that cpu node? Or did you mean once per cpu core? -- Thanks and Regards Srikar Dronamraju