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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 D3308C433ED for ; Sat, 1 May 2021 22:07:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A964A61466 for ; Sat, 1 May 2021 22:07:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231736AbhEAWEu (ORCPT ); Sat, 1 May 2021 18:04:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:53156 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229912AbhEAWEs (ORCPT ); Sat, 1 May 2021 18:04:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619906638; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Js+GaB17CMiaTOtjm6gUVj7FN3DfTKpTGNOBnmvNMzg=; b=YHMilZikUgjtH21jGpnwIJvZfyiU5G8/l/M/mdwsq58tSozXsp6ak7C4IrBxmazG+yC7X1 IDQu754bu61CP8KV+F+KQn6RlaFYdamu1w7ngUTIRJghwAZQ56DIlPT0rIrNvOxWv27xwG hZtdueMPZDDbE/HlnGOnrR4AW1l0Qbs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-604-zrr61oAkOaeaeyWmK0PJbg-1; Sat, 01 May 2021 18:03:53 -0400 X-MC-Unique: zrr61oAkOaeaeyWmK0PJbg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BF767801B20; Sat, 1 May 2021 22:03:51 +0000 (UTC) Received: from ovpn-112-143.rdu2.redhat.com (ovpn-112-143.rdu2.redhat.com [10.10.112.143]) by smtp.corp.redhat.com (Postfix) with ESMTP id 634EB5D6AB; Sat, 1 May 2021 22:03:48 +0000 (UTC) Message-ID: <7b796a085b0bc638c9df70d3a20718f8d1d776c8.camel@redhat.com> Subject: Re: [PATCH v2 0/3] newidle_balance() PREEMPT_RT latency mitigations From: Scott Wood To: Vincent Guittot Cc: Ingo Molnar , Peter Zijlstra , Dietmar Eggemann , Steven Rostedt , Mel Gorman , Valentin Schneider , linux-kernel , linux-rt-users , Sebastian Andrzej Siewior , Thomas Gleixner Date: Sat, 01 May 2021 17:03:47 -0500 In-Reply-To: References: <20210428232821.2506201-1-swood@redhat.com> Organization: Red Hat Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2021-04-29 at 09:12 +0200, Vincent Guittot wrote: > Hi Scott, > > On Thu, 29 Apr 2021 at 01:28, Scott Wood wrote: > > These patches mitigate latency caused by newidle_balance() on large > > systems when PREEMPT_RT is enabled, by enabling interrupts when the lock > > is dropped, and exiting early at various points if an RT task is > > runnable > > on the current CPU. > > > > On a system with 128 CPUs, these patches dropped latency (as measured by > > a 12 hour rteval run) from 1045us to 317us (when applied to > > 5.12.0-rc3-rt3). > > The patch below has been queued for v5.13 and removed the update of > blocked load what seemed to be the major reason for long preempt/irq > off during newly idle balance: > https://lore.kernel.org/lkml/20210224133007.28644-1-vincent.guittot@linaro.org/ > > I would be curious to see how it impacts your cases I still get 1000+ ms latencies with those patches applied. -Scott