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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 61B8BC35249 for ; Wed, 5 Feb 2020 04:20:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 36D92217F4 for ; Wed, 5 Feb 2020 04:20:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727922AbgBEEUM (ORCPT ); Tue, 4 Feb 2020 23:20:12 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:26772 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727832AbgBEEUL (ORCPT ); Tue, 4 Feb 2020 23:20:11 -0500 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0154IgxB065034; Tue, 4 Feb 2020 23:20:01 -0500 Received: from ppma04dal.us.ibm.com (7a.29.35a9.ip4.static.sl-reverse.com [169.53.41.122]) by mx0a-001b2d01.pphosted.com with ESMTP id 2xyhn27wn4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 04 Feb 2020 23:20:00 -0500 Received: from pps.filterd (ppma04dal.us.ibm.com [127.0.0.1]) by ppma04dal.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id 0154F1Iw002400; Wed, 5 Feb 2020 04:20:00 GMT Received: from b01cxnp23034.gho.pok.ibm.com (b01cxnp23034.gho.pok.ibm.com [9.57.198.29]) by ppma04dal.us.ibm.com with ESMTP id 2xykc99w38-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 05 Feb 2020 04:20:00 +0000 Received: from b01ledav001.gho.pok.ibm.com (b01ledav001.gho.pok.ibm.com [9.57.199.106]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0154JxPk40894772 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 5 Feb 2020 04:19:59 GMT Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3A3F02805A; Wed, 5 Feb 2020 04:19:59 +0000 (GMT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F06EA28058; Wed, 5 Feb 2020 04:19:58 +0000 (GMT) Received: from sofia.ibm.com (unknown [9.124.31.110]) by b01ledav001.gho.pok.ibm.com (Postfix) with ESMTP; Wed, 5 Feb 2020 04:19:58 +0000 (GMT) Received: by sofia.ibm.com (Postfix, from userid 1000) id 26C4F2E3006; Wed, 5 Feb 2020 09:49:56 +0530 (IST) Date: Wed, 5 Feb 2020 09:49:56 +0530 From: Gautham R Shenoy To: "Naveen N. Rao" Cc: ego@linux.vnet.ibm.com, Kamalesh Babulal , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Michael Ellerman , Nathan Lynch , Vaidyanathan Srinivasan , Tyrel Datwyler Subject: Re: [PATCH 2/3] powerpc/sysfs: Show idle_purr and idle_spurr for every CPU Message-ID: <20200205041956.GA5401@in.ibm.com> Reply-To: ego@linux.vnet.ibm.com References: <1574856072-30972-1-git-send-email-ego@linux.vnet.ibm.com> <1574856072-30972-3-git-send-email-ego@linux.vnet.ibm.com> <1575564547.si4rk0s96p.naveen@linux.ibm.com> <20200203045013.GC13468@in.ibm.com> <1580802180.jpxk9s8apz.naveen@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1580802180.jpxk9s8apz.naveen@linux.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-04_09:2020-02-04,2020-02-04 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 malwarescore=0 suspectscore=0 phishscore=0 clxscore=1015 adultscore=0 mlxlogscore=999 bulkscore=0 spamscore=0 lowpriorityscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002050034 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Naveen, On Tue, Feb 04, 2020 at 01:22:19PM +0530, Naveen N. Rao wrote: > Gautham R Shenoy wrote: > >Hi Naveen, > > > >On Thu, Dec 05, 2019 at 10:23:58PM +0530, Naveen N. Rao wrote: > >>>diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c > >>>index 80a676d..42ade55 100644 > >>>--- a/arch/powerpc/kernel/sysfs.c > >>>+++ b/arch/powerpc/kernel/sysfs.c > >>>@@ -1044,6 +1044,36 @@ static ssize_t show_physical_id(struct device *dev, > >>> } > >>> static DEVICE_ATTR(physical_id, 0444, show_physical_id, NULL); > >>> > >>>+static ssize_t idle_purr_show(struct device *dev, > >>>+ struct device_attribute *attr, char *buf) > >>>+{ > >>>+ struct cpu *cpu = container_of(dev, struct cpu, dev); > >>>+ unsigned int cpuid = cpu->dev.id; > >>>+ struct lppaca *cpu_lppaca_ptr = paca_ptrs[cpuid]->lppaca_ptr; > >>>+ u64 idle_purr_cycles = be64_to_cpu(cpu_lppaca_ptr->wait_state_cycles); > >>>+ > >>>+ return sprintf(buf, "%llx\n", idle_purr_cycles); > >>>+} > >>>+static DEVICE_ATTR_RO(idle_purr); > >>>+ > >>>+DECLARE_PER_CPU(u64, idle_spurr_cycles); > >>>+static ssize_t idle_spurr_show(struct device *dev, > >>>+ struct device_attribute *attr, char *buf) > >>>+{ > >>>+ struct cpu *cpu = container_of(dev, struct cpu, dev); > >>>+ unsigned int cpuid = cpu->dev.id; > >>>+ u64 *idle_spurr_cycles_ptr = per_cpu_ptr(&idle_spurr_cycles, cpuid); > >> > >>Is it possible for a user to read stale values if a particular cpu is in an > >>extended cede? Is it possible to use smp_call_function_single() to force the > >>cpu out of idle? > > > >Yes, if the CPU whose idle_spurr cycle is being read is still in idle, > >then we will miss reporting the delta spurr cycles for this last > >idle-duration. Yes, we can use an smp_call_function_single(), though > >that will introduce IPI noise. How often will idle_[s]purr be read ? > > Since it is possible for a cpu to go into extended cede for multiple seconds > during which time it is possible to mis-report utilization, I think it is > better to ensure that the sysfs interface for idle_[s]purr report the proper > values through use of IPI. > Fair enough. > With repect to lparstat, the read interval is user-specified and just gets > passed onto sleep(). Ok. So I guess currently you will be sending smp_call_function every time you read a PURR and SPURR. That number will now increase by 2 times when we read idle_purr and idle_spurr. > > - Naveen > -- Thanks and Regards gautham.