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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7171C761A6 for ; Thu, 30 Mar 2023 18:54:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231439AbjC3Sys (ORCPT ); Thu, 30 Mar 2023 14:54:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229505AbjC3Syn (ORCPT ); Thu, 30 Mar 2023 14:54:43 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77C05DBD1 for ; Thu, 30 Mar 2023 11:53:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680202435; 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: in-reply-to:in-reply-to:references:references; bh=yILtE8G0wRpMYBAf60dk5xAKt3MM/0au1zweuUxeqC8=; b=QIJ71ERfbwrnXMzQG+p0Hq8rcMnghIdkBvJ6J30GYzIIRZQbsBZ2arjmrWmhjMRwL7LsaH W9jP4laVXGDdW5SuSayn/+KQRSrdlW4gEJNoUjrSdxiTBFoauhuRg8P0m5JMxH4v4GGPH6 FiVYMWj6BLkCXBOBrrwnPcwYS4eM9Xk= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-148-wFNaXMt2O9-prAhtlP8RLw-1; Thu, 30 Mar 2023 14:53:51 -0400 X-MC-Unique: wFNaXMt2O9-prAhtlP8RLw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id F39B6811E7C; Thu, 30 Mar 2023 18:53:49 +0000 (UTC) Received: from tpad.localdomain (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B4DE04020C82; Thu, 30 Mar 2023 18:53:49 +0000 (UTC) Received: by tpad.localdomain (Postfix, from userid 1000) id 3C6FB4038C70D; Thu, 30 Mar 2023 12:21:22 -0300 (-03) Date: Thu, 30 Mar 2023 12:21:22 -0300 From: Marcelo Tosatti To: Michal Hocko Cc: Frederic Weisbecker , Frederic Weisbecker , Andrew Morton , Leonardo Bras , Peter Zijlstra , Thomas Gleixner , Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , LKML , linux-mm@kvack.org Subject: Re: [PATCH 1/2] sched/isolation: Add cpu_is_isolated() API Message-ID: References: <20230317134448.11082-1-mhocko@kernel.org> <20230317134448.11082-2-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 30, 2023 at 03:28:52PM +0200, Michal Hocko wrote: > > > Is this a best practice documented anywhere or it just happens to be > > > the case with workloads you deal with? > > > > Option 2. However Frederic seems interested in matching the exported > > toggles with the known use-cases classes. > > > > For example, for this guide: > > http://www.comfilewiki.co.kr/en/doku.php?id=comfilepi:improving_real-time_performance:index > > > > Using nohz_full= would be a benefit (and its not being currently set, > > perhaps due to not knowing all the options?). > > > > http://www.comfilewiki.co.kr/en/doku.php?id=comfilepi:improving_real-time_performance:index > > > > > > AFAIU the workloads for which disabling nohz_full= is a benefit are those > > where the switching between nohz full mode and sched tick enabled mode > > and vice-versa (which involve programming the local timer) happens > > often and is therefore avoidable? For example switching between 1 > > runnable task and more than 1 runnable task (and vice versa). > > The patch from Frederic is testing for both. You seem to be arguing to > reduce the test and I still do not understand why. Sure some workloads > (following the above) will likely use nohz_full= as well but does it > make sense to build that expectation into the higher level logic? What > is an actual benefit? Just thinking of simpler code. Feel free to maintain the patch as-is if you see fit.