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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 77550C433DF for ; Tue, 28 Jul 2020 19:21:41 +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 DAA5A20656 for ; Tue, 28 Jul 2020 19:21:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DAA5A20656 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.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 4BGRPH2CWczDr3M for ; Wed, 29 Jul 2020 05:21:39 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=nathanl@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.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 4BGRLW4VmNzDr1N for ; Wed, 29 Jul 2020 05:19:14 +1000 (AEST) Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 06SJ2aFu195957 for ; Tue, 28 Jul 2020 15:19:10 -0400 Received: from ppma01wdc.us.ibm.com (fd.55.37a9.ip4.static.sl-reverse.com [169.55.85.253]) by mx0b-001b2d01.pphosted.com with ESMTP id 32hrnn4gt2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 28 Jul 2020 15:19:10 -0400 Received: from pps.filterd (ppma01wdc.us.ibm.com [127.0.0.1]) by ppma01wdc.us.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 06SJG07p005024 for ; Tue, 28 Jul 2020 19:19:09 GMT Received: from b03cxnp08027.gho.boulder.ibm.com (b03cxnp08027.gho.boulder.ibm.com [9.17.130.19]) by ppma01wdc.us.ibm.com with ESMTP id 32gcyckva5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 28 Jul 2020 19:19:09 +0000 Received: from b03ledav004.gho.boulder.ibm.com (b03ledav004.gho.boulder.ibm.com [9.17.130.235]) by b03cxnp08027.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 06SJJ6PQ9831076 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 28 Jul 2020 19:19:06 GMT Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A157E7805C; Tue, 28 Jul 2020 19:19:08 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 69BC078064; Tue, 28 Jul 2020 19:19:08 +0000 (GMT) Received: from localhost (unknown [9.65.227.150]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 28 Jul 2020 19:19:08 +0000 (GMT) From: Nathan Lynch To: Laurent Dufour Subject: Re: [PATCH] powerpc/pseries: explicitly reschedule during drmem_lmb list traversal In-Reply-To: References: <20200728173741.717372-1-nathanl@linux.ibm.com> Date: Tue, 28 Jul 2020 14:19:07 -0500 Message-ID: <878sf31m8k.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-28_15:2020-07-28, 2020-07-28 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=1 mlxlogscore=999 adultscore=0 clxscore=1015 impostorscore=0 phishscore=0 mlxscore=0 spamscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007280131 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: tyreld@linux.ibm.com, cheloha@linux.ibm.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Laurent, Laurent Dufour writes: > Le 28/07/2020 =C3=A0 19:37, Nathan Lynch a =C3=A9crit=C2=A0: >> The drmem lmb list can have hundreds of thousands of entries, and >> unfortunately lookups take the form of linear searches. As long as >> this is the case, traversals have the potential to monopolize the CPU >> and provoke lockup reports, workqueue stalls, and the like unless >> they explicitly yield. >>=20 >> Rather than placing cond_resched() calls within various >> for_each_drmem_lmb() loop blocks in the code, put it in the iteration >> expression of the loop macro itself so users can't omit it. > > Is that not too much to call cond_resched() on every LMB? > > Could that be less frequent, every 10, or 100, I don't really know ? Everything done within for_each_drmem_lmb is relatively heavyweight already. E.g. calling dlpar_remove_lmb()/dlpar_add_lmb() can take dozens of milliseconds. I don't think cond_resched() is an expensive check in this context.