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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 32A7DC4332B for ; Mon, 23 Mar 2020 14:26:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 108B7206F8 for ; Mon, 23 Mar 2020 14:26:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727120AbgCWO0j (ORCPT ); Mon, 23 Mar 2020 10:26:39 -0400 Received: from foss.arm.com ([217.140.110.172]:50176 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725776AbgCWO0i (ORCPT ); Mon, 23 Mar 2020 10:26:38 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B28771FB; Mon, 23 Mar 2020 07:26:37 -0700 (PDT) Received: from [192.168.1.19] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A7CEF3F52E; Mon, 23 Mar 2020 07:26:36 -0700 (PDT) Subject: Re: [PATCH v2 3/9] sched: Remove checks against SD_LOAD_BALANCE To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org References: <20200311181601.18314-1-valentin.schneider@arm.com> <20200311181601.18314-4-valentin.schneider@arm.com> From: Dietmar Eggemann Message-ID: <5decd96b-6fe0-3c35-4609-59378a0c8621@arm.com> Date: Mon, 23 Mar 2020 15:26:35 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19.03.20 13:05, Valentin Schneider wrote: > > On Thu, Mar 19 2020, Dietmar Eggemann wrote: >> On 11.03.20 19:15, Valentin Schneider wrote: [...] > Your comments make me realize that changelog isn't great, what about the > following? > > --- > > The SD_LOAD_BALANCE flag is set unconditionally for all domains in > sd_init(). By making the sched_domain->flags syctl interface read-only, we > have removed the last piece of code that could clear that flag - as such, > it will now be always present. Rather than to keep carrying it along, we > can work towards getting rid of it entirely. > > cpusets don't need it because they can make CPUs be attached to the NULL > domain (e.g. cpuset with sched_load_balance=0), or to a partitionned s/partitionned/partitioned > root_domain, i.e. a sched_domain hierarchy that doesn't span the entire > system (e.g. root cpuset with sched_load_balance=0 and sibling cpusets with > sched_load_balance=1). > > isolcpus apply the same "trick": isolated CPUs are explicitly taken out of > the sched_domain rebuild (using housekeeping_cpumask()), so they get the > NULL domain treatment as well. > > Remove the checks against SD_LOAD_BALANCE. Sounds better to me: Essentially, I was referring to examples like: Hikey960 - 2x4 (A) exclusive cpusets: root@h960:/sys/fs/cgroup/cpuset# mkdir cs1 root@h960:/sys/fs/cgroup/cpuset# echo 1 > cs1/cpuset.cpu_exclusive root@h960:/sys/fs/cgroup/cpuset# echo 0 > cs1/cpuset.mems root@h960:/sys/fs/cgroup/cpuset# echo 0-2 > cs1/cpuset.cpus root@h960:/sys/fs/cgroup/cpuset# mkdir cs2 root@h960:/sys/fs/cgroup/cpuset# echo 1 > cs2/cpuset.cpu_exclusive root@h960:/sys/fs/cgroup/cpuset# echo 0 > cs2/cpuset.mems root@h960:/sys/fs/cgroup/cpuset# echo 3-5 > cs2/cpuset.cpus root@h960:/sys/fs/cgroup/cpuset# echo 0 > cpuset.sched_load_balance root@h960:/proc/sys/kernel# tree -d sched_domain ├── cpu0 │ └── domain0 ├── cpu1 │ └── domain0 ├── cpu2 │ └── domain0 ├── cpu3 │ └── domain0 ├── cpu4 │ ├── domain0 │ └── domain1 ├── cpu5 │ ├── domain0 │ └── domain1 ├── cpu6 └── cpu7 (B) non-exclusive cpuset: root@h960:/sys/fs/cgroup/cpuset# echo 0 > cpuset.sched_load_balance [ 8661.240385] CPU1 attaching NULL sched-domain. [ 8661.244802] CPU2 attaching NULL sched-domain. [ 8661.249255] CPU3 attaching NULL sched-domain. [ 8661.253623] CPU4 attaching NULL sched-domain. [ 8661.257989] CPU5 attaching NULL sched-domain. [ 8661.262363] CPU6 attaching NULL sched-domain. [ 8661.266730] CPU7 attaching NULL sched-domain. root@h960:/sys/fs/cgroup/cpuset# mkdir cs1 root@h960:/sys/fs/cgroup/cpuset# echo 0-5 > cs1/cpuset.cpus root@h960:/proc/sys/kernel# tree -d sched_domain ├── cpu0 │ ├── domain0 │ └── domain1 ├── cpu1 │ ├── domain0 │ └── domain1 ├── cpu2 │ ├── domain0 │ └── domain1 ├── cpu3 │ ├── domain0 │ └── domain1 ├── cpu4 │ ├── domain0 │ └── domain1 ├── cpu5 │ ├── domain0 │ └── domain1 ├── cpu6 └── cpu7