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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_PASS 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 3D779C10F11 for ; Thu, 11 Apr 2019 00:16:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05AB620850 for ; Thu, 11 Apr 2019 00:16:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="LEYe+K66" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726825AbfDKAP7 (ORCPT ); Wed, 10 Apr 2019 20:15:59 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:45926 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726023AbfDKAP7 (ORCPT ); Wed, 10 Apr 2019 20:15:59 -0400 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x3B00DAg174755; Thu, 11 Apr 2019 00:15:21 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=ZE0Izvf5nzZxCJ/OcSAToK5lGjnoIFnhYkDGbZEZ6ZE=; b=LEYe+K66LGKaugCFdAnSWj2H5td93cEHq144Ekjj7jVVAnh3rzH4oL+uqgXaXIdgKKBC +/rP7K98uDNRpFyPn4+oW5jhx+mm0+MIlf6/puyjzZpR8ohPo1bMw3NnhmB8y5k6OHI6 odNAg50CrgwSHP/QuvstkKNjXkpgHkRgNe2XgakQbj6Hl8bbRxdwAcO2D7f55hpGr4h6 l+ShaB/5N49HH9v04JptHWkF+GUmy5PCHHZEfzGcIL0bt6YoHh7bacWHwMDYDp/1lxQO PqKOyXj3MpsKMw8iSOo6Y5A6XtDB5LvzhsjM7aNHkYMyMJGZijXdqhnNXLH2vpbSIacj Hw== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2130.oracle.com with ESMTP id 2rphmep4eu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 11 Apr 2019 00:15:21 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x3B0Dv0f003434; Thu, 11 Apr 2019 00:15:20 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userp3020.oracle.com with ESMTP id 2rpkek6fgr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 11 Apr 2019 00:15:20 +0000 Received: from abhmp0006.oracle.com (abhmp0006.oracle.com [141.146.116.12]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x3B0FENT001490; Thu, 11 Apr 2019 00:15:19 GMT Received: from [10.132.91.175] (/10.132.91.175) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 10 Apr 2019 17:15:14 -0700 Subject: Re: [RFC][PATCH 13/16] sched: Add core wide task selection and scheduling. To: Julien Desfossez , Peter Zijlstra , mingo@kernel.org, tglx@linutronix.de, pjt@google.com, tim.c.chen@linux.intel.com, torvalds@linux-foundation.org Cc: linux-kernel@vger.kernel.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Vineeth Pillai , Nishanth Aravamudan , Aaron Lu References: <20190218173514.667598558@infradead.org> <1554835135-11814-1-git-send-email-jdesfossez@digitalocean.com> From: Subhra Mazumdar Message-ID: <3514bb97-33bc-3a14-3f15-767682b2f035@oracle.com> Date: Wed, 10 Apr 2019 17:11:59 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <1554835135-11814-1-git-send-email-jdesfossez@digitalocean.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9223 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904100157 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9223 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904100157 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/9/19 11:38 AM, Julien Desfossez wrote: > We found the source of the major performance regression we discussed > previously. It turns out there was a pattern where a task (a kworker in this > case) could be woken up, but the core could still end up idle before that > task had a chance to run. > > Example sequence, cpu0 and cpu1 and siblings on the same core, task1 and > task2 are in the same cgroup with the tag enabled (each following line > happens in the increasing order of time): > - task1 running on cpu0, task2 running on cpu1 > - sched_waking(kworker/0, target_cpu=cpu0) > - task1 scheduled out of cpu0 > - kworker/0 cannot run on cpu0 because of task2 is still running on cpu1 > cpu0 is idle > - task2 scheduled out of cpu1 > - cpu1 doesn’t select kworker/0 for cpu0, because the optimization path ends > the task selection if core_cookie is NULL for currently selected process > and the cpu1’s runqueue. > - cpu1 is idle > --> both siblings are idle but kworker/0 is still in the run queue of cpu0. > Cpu0 may stay idle for longer if it goes deep idle. > > With the fix below, we ensure to send an IPI to the sibling if it is idle > and has tasks waiting in its runqueue. > This fixes the performance issue we were seeing. > > Now here is what we can measure with a disk write-intensive benchmark: > - no performance impact with enabling core scheduling without any tagged > task, > - 5% overhead if one tagged task is competing with an untagged task, > - 10% overhead if 2 tasks tagged with a different tag are competing > against each other. > > We are starting more scaling tests, but this is very encouraging ! > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index e1fa10561279..02c862a5e973 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3779,7 +3779,22 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > > trace_printk("unconstrained pick: %s/%d %lx\n", > next->comm, next->pid, next->core_cookie); > + rq->core_pick = NULL; > > + /* > + * If the sibling is idling, we might want to wake it > + * so that it can check for any runnable but blocked tasks > + * due to previous task matching. > + */ > + for_each_cpu(j, smt_mask) { > + struct rq *rq_j = cpu_rq(j); > + rq_j->core_pick = NULL; > + if (j != cpu && is_idle_task(rq_j->curr) && rq_j->nr_running) { > + resched_curr(rq_j); > + trace_printk("IPI(%d->%d[%d]) idle preempt\n", > + cpu, j, rq_j->nr_running); > + } > + } > goto done; > } > I see similar improvement with this patch as removing the condition I earlier mentioned. So that's not needed. I also included the patch for the priority fix. For 2 DB instances, HT disabling stands at -22% for 32 users (from earlier emails). 1 DB instance users  baseline   %idle    core_sched %idle 16     1          84       -4.9% 84 24     1          76       -6.7% 75 32     1          69       -2.4% 69 2 DB instance users  baseline   %idle    core_sched %idle 16     1          66       -19.5% 69 24     1          54       -9.8% 57 32     1          42       -27.2%        48