From patchwork Wed Jun 10 21:05:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tom Hromatka X-Patchwork-Id: 11598917 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A6B3314E3 for ; Wed, 10 Jun 2020 21:06:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8941720842 for ; Wed, 10 Jun 2020 21:06:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="JCM8LL68" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726180AbgFJVGH (ORCPT ); Wed, 10 Jun 2020 17:06:07 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:54588 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726134AbgFJVGF (ORCPT ); Wed, 10 Jun 2020 17:06:05 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 05AKqv25085289; Wed, 10 Jun 2020 21:05:52 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=corp-2020-01-29; bh=ltkLJIPe4dHdcnuDRbQdb6ZEMq/7yblSuuxzoI9Jykk=; b=JCM8LL68Y+dpHTScVfDL+XoLxtpaOAlI5BCBEqArSKCfUEtHnKzGT6P4xcRrmuM5VVfU CHzv1yXtiogAKFEPrcT2pTD5qtSrfd9QWk02QWZg3KhNBb3vuvJq7Q2GEw7ZSqDufc4L q7psPI6OAyf2RZaNNJuRbr62P8PNekX2R1K7/hgvLFiiagHzrCNPVCF8tDR/BFLbN2Lj 83/2NeOiSz5asZ9OHvaicKdeedBXclPatsFzZPiKlxK6LmSzcS+pjpxNXSBGxELb7Dwo i5mlWKciT/na1n6W7ENywb/K5UWJXEeuGOUScf8VgPEd4PqbMYHaiKY2ewYaucovn/ul uQ== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2120.oracle.com with ESMTP id 31g3sn4ffm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 10 Jun 2020 21:05:52 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 05AKiSOn132390; Wed, 10 Jun 2020 21:05:52 GMT Received: from pps.reinject (localhost [127.0.0.1]) by userp3020.oracle.com with ESMTP id 31gmwtve42-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 10 Jun 2020 21:05:52 +0000 Received: from userp3020.oracle.com (userp3020.oracle.com [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 05AL5o8e021995; Wed, 10 Jun 2020 21:05:52 GMT Received: from localhost.localdomain (dhcp-10-65-148-96.vpn.oracle.com [10.65.148.96]) by userp3020.oracle.com with ESMTP id 31gmwtve2s-3; Wed, 10 Jun 2020 21:05:51 +0000 From: Tom Hromatka To: tom.hromatka@oracle.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: fweisbec@gmail.com, tglx@linutronix.de, mingo@kernel.org, adobriyan@gmail.com Subject: [PATCH 2/2] /proc/stat: Simplify iowait and idle calculations when cpu is offline Date: Wed, 10 Jun 2020 15:05:49 -0600 Message-Id: <20200610210549.61193-3-tom.hromatka@oracle.com> X-Mailer: git-send-email 2.25.3 In-Reply-To: <20200610210549.61193-1-tom.hromatka@oracle.com> References: <20200610210549.61193-1-tom.hromatka@oracle.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9648 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 impostorscore=0 cotscore=-2147483648 suspectscore=0 spamscore=0 bulkscore=0 malwarescore=0 phishscore=0 mlxscore=0 mlxlogscore=999 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006100154 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org A customer reported that when a cpu goes offline, the iowait and idle times reported in /proc/stat will sometimes spike. This is being caused by a different data source being used for these values when a cpu is offline. Prior to this patch: put the system under heavy load so that there is little idle time user nice system idle iowait cpu 109515 17 32111 220686 607 take cpu1 offline user nice system idle iowait cpu 113742 17 32721 220724 612 bring cpu1 back online user nice system idle iowait cpu 118332 17 33430 220687 607 To prevent this, let's use the same data source whether a cpu is online or not. With this patch: put the system under heavy load so that there is little idle time user nice system idle iowait cpu 14096 16 4646 157687 426 take cpu1 offline user nice system idle iowait cpu 21614 16 7179 157687 426 bring cpu1 back online user nice system idle iowait cpu 27362 16 9555 157688 426 Signed-off-by: Tom Hromatka --- fs/proc/stat.c | 24 ++++++------------------ 1 file changed, 6 insertions(+), 18 deletions(-) diff --git a/fs/proc/stat.c b/fs/proc/stat.c index 46b3293015fe..35b92539e711 100644 --- a/fs/proc/stat.c +++ b/fs/proc/stat.c @@ -47,32 +47,20 @@ static u64 get_iowait_time(struct kernel_cpustat *kcs, int cpu) static u64 get_idle_time(struct kernel_cpustat *kcs, int cpu) { - u64 idle, idle_usecs = -1ULL; + u64 idle, idle_usecs; - if (cpu_online(cpu)) - idle_usecs = get_cpu_idle_time_us(cpu, NULL); - - if (idle_usecs == -1ULL) - /* !NO_HZ or cpu offline so we can rely on cpustat.idle */ - idle = kcs->cpustat[CPUTIME_IDLE]; - else - idle = idle_usecs * NSEC_PER_USEC; + idle_usecs = get_cpu_idle_time_us(cpu, NULL); + idle = idle_usecs * NSEC_PER_USEC; return idle; } static u64 get_iowait_time(struct kernel_cpustat *kcs, int cpu) { - u64 iowait, iowait_usecs = -1ULL; - - if (cpu_online(cpu)) - iowait_usecs = get_cpu_iowait_time_us(cpu, NULL); + u64 iowait, iowait_usecs; - if (iowait_usecs == -1ULL) - /* !NO_HZ or cpu offline so we can rely on cpustat.iowait */ - iowait = kcs->cpustat[CPUTIME_IOWAIT]; - else - iowait = iowait_usecs * NSEC_PER_USEC; + iowait_usecs = get_cpu_iowait_time_us(cpu, NULL); + iowait = iowait_usecs * NSEC_PER_USEC; return iowait; }