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=-5.8 required=3.0 tests=BAYES_00,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 8F13CC48BE5 for ; Thu, 10 Jun 2021 19:00:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E8A5613B0 for ; Thu, 10 Jun 2021 19:00:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230291AbhFJTCq (ORCPT ); Thu, 10 Jun 2021 15:02:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230059AbhFJTCo (ORCPT ); Thu, 10 Jun 2021 15:02:44 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF7D6C061574; Thu, 10 Jun 2021 12:00:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=xTRjHtkMVfiEz4i7gVCu050JHA1BAAViAhxBjNTqnr0=; b=v0ermCJCsvrKcJozDIgJaQ9mAs QK/N1tf1IVJBqXRoU2Zjqfd+0nWnmqmjfB7N0ptRxKQd/2eFgSKzsRLMxX9DTKtCZydrecLkoxpLW 5T7E7oDDx3F/yKl//Z2wdkyNvkSZXpc8J+xNo/jsDiDMyp49ayMBMqljhsnuO6Qdg+S9faxM3hg1x 01xaJ91axH5I7Hi6Kylz6tgA2IxY/nZKF67bPkr6jN6Tvx9t718+/WOotzmIkTl9/zxWQf5MeKyXk RZCP/M4Xkx4p+UsrO0GCP+fqlm+fQN9Nhe5RlpXZCgaJQeW2k3WEICEjPExfpHYhZ9IFs0fDN7dwk uwoPK1uQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lrPuU-001yKc-6y; Thu, 10 Jun 2021 19:00:14 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 8F35C3001E3; Thu, 10 Jun 2021 21:00:09 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6FFA3200F8CB3; Thu, 10 Jun 2021 21:00:09 +0200 (CEST) Date: Thu, 10 Jun 2021 21:00:09 +0200 From: Peter Zijlstra To: Waiman Long Cc: Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Roman Gushchin , Phil Auld , Juri Lelli Subject: Re: [PATCH 2/5] cgroup/cpuset: Add new cpus.partition type with no load balancing Message-ID: References: <20210603212416.25934-1-longman@redhat.com> <20210603212416.25934-3-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210603212416.25934-3-longman@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 03, 2021 at 05:24:13PM -0400, Waiman Long wrote: > Cpuset v1 uses the sched_load_balance control file to determine if load > balancing should be enabled. Cpuset v2 gets rid of sched_load_balance > as its use may require disabling load balancing at cgroup root. > > For workloads that require very low latency like DPDK, the latency > jitters caused by periodic load balancing may exceed the desired > latency limit. > > When cpuset v2 is in use, the only way to avoid this latency cost is to > use the "isolcpus=" kernel boot option to isolate a set of CPUs. After > the kernel boot, however, there is no way to add or remove CPUs from > this isolated set. For workloads that are more dynamic in nature, that > means users have to provision enough CPUs for the worst case situation > resulting in excess idle CPUs. Also, can we change isolcpus to create a default cgroup hierarchy instead of being the fugly hack that it is? I really hate isolcpus with a passion, it needs to die. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 2/5] cgroup/cpuset: Add new cpus.partition type with no load balancing Date: Thu, 10 Jun 2021 21:00:09 +0200 Message-ID: References: <20210603212416.25934-1-longman@redhat.com> <20210603212416.25934-3-longman@redhat.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=xTRjHtkMVfiEz4i7gVCu050JHA1BAAViAhxBjNTqnr0=; b=v0ermCJCsvrKcJozDIgJaQ9mAs QK/N1tf1IVJBqXRoU2Zjqfd+0nWnmqmjfB7N0ptRxKQd/2eFgSKzsRLMxX9DTKtCZydrecLkoxpLW 5T7E7oDDx3F/yKl//Z2wdkyNvkSZXpc8J+xNo/jsDiDMyp49ayMBMqljhsnuO6Qdg+S9faxM3hg1x 01xaJ91axH5I7Hi6Kylz6tgA2IxY/nZKF67bPkr6jN6Tvx9t718+/WOotzmIkTl9/zxWQf5MeKyXk RZCP/M4Xkx4p+UsrO0GCP+fqlm+fQN9Nhe5RlpXZCgaJQeW2k3WEICEjPExfpHYhZ9IFs0fDN7dwk uwoPK1uQ==; Content-Disposition: inline In-Reply-To: <20210603212416.25934-3-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Waiman Long Cc: Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kselftest-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrew Morton , Roman Gushchin , Phil Auld , Juri Lelli On Thu, Jun 03, 2021 at 05:24:13PM -0400, Waiman Long wrote: > Cpuset v1 uses the sched_load_balance control file to determine if load > balancing should be enabled. Cpuset v2 gets rid of sched_load_balance > as its use may require disabling load balancing at cgroup root. > > For workloads that require very low latency like DPDK, the latency > jitters caused by periodic load balancing may exceed the desired > latency limit. > > When cpuset v2 is in use, the only way to avoid this latency cost is to > use the "isolcpus=" kernel boot option to isolate a set of CPUs. After > the kernel boot, however, there is no way to add or remove CPUs from > this isolated set. For workloads that are more dynamic in nature, that > means users have to provision enough CPUs for the worst case situation > resulting in excess idle CPUs. Also, can we change isolcpus to create a default cgroup hierarchy instead of being the fugly hack that it is? I really hate isolcpus with a passion, it needs to die.