From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v8 3/6] cpuset: Add cpuset.sched.load_balance flag to v2 Date: Thu, 24 May 2018 17:43:41 +0200 Message-ID: <20180524154341.GJ12198@hirez.programming.kicks-ass.net> References: <1526590545-3350-1-git-send-email-longman@redhat.com> <1526590545-3350-4-git-send-email-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=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=pBHJEC6rCvWa/ECQO/49DsKWJe35kRl+AcunCcpTkSo=; b=E0al/HiVlN6p7AhoCRcGvoUDf z0SHCsDW72wsgOjGjMjhCx9l+mIAs2xioQVDyel8wFXRF/AUILkwLSRhK3RxKsaqnnhWnYHRrrp7O ZvuAu9UzfmFJPMySBbPmpv0+n5yncqiZiMh4pcnzNH/swiAyTWGc46+m7tU85GLkq8Dlj/YA4xNRD BioyQy/JybOw9jogtZa/cRrZjRAbEssqPC3CTcod5FauldtBTfViuVN3yq+ubf+AWX2kq2ktLezob Yt/jalSdpkKJ8srLYbDMmb7X9PlicC6MwRqQ59HRbuSInI8glfvACanNhiT3dFRkKnu/PQYUWHe61 Content-Disposition: inline In-Reply-To: <1526590545-3350-4-git-send-email-longman@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Waiman Long Cc: Tejun Heo , Li Zefan , Johannes Weiner , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, Mike Galbraith , torvalds@linux-foundation.org, Roman Gushchin , Juri Lelli On Thu, May 17, 2018 at 04:55:42PM -0400, Waiman Long wrote: > The sched.load_balance flag is needed to enable CPU isolation similar to > what can be done with the "isolcpus" kernel boot parameter. Its value > can only be changed in a scheduling domain with no child cpusets. On > a non-scheduling domain cpuset, the value of sched.load_balance is > inherited from its parent. > > This flag is set by the parent and is not delegatable. > > Signed-off-by: Waiman Long > --- > Documentation/cgroup-v2.txt | 24 ++++++++++++++++++++ > kernel/cgroup/cpuset.c | 53 +++++++++++++++++++++++++++++++++++++++++---- > 2 files changed, 73 insertions(+), 4 deletions(-) > > diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt > index 54d9e22..071b634d 100644 > --- a/Documentation/cgroup-v2.txt > +++ b/Documentation/cgroup-v2.txt > @@ -1536,6 +1536,30 @@ Cpuset Interface Files > CPUs of the parent cgroup. Once it is set, this flag cannot be > cleared if there are any child cgroups with cpuset enabled. > > + A parent cgroup cannot distribute all its CPUs to child > + scheduling domain cgroups unless its load balancing flag is > + turned off. > + > + cpuset.sched.load_balance > + A read-write single value file which exists on non-root > + cpuset-enabled cgroups. It is a binary value flag that accepts > + either "0" (off) or a non-zero value (on). This flag is set > + by the parent and is not delegatable. > + > + When it is on, tasks within this cpuset will be load-balanced > + by the kernel scheduler. Tasks will be moved from CPUs with > + high load to other CPUs within the same cpuset with less load > + periodically. > + > + When it is off, there will be no load balancing among CPUs on > + this cgroup. Tasks will stay in the CPUs they are running on > + and will not be moved to other CPUs. > + > + The initial value of this flag is "1". This flag is then > + inherited by child cgroups with cpuset enabled. Its state > + can only be changed on a scheduling domain cgroup with no > + cpuset-enabled children. I'm confused... why exactly do we have both domain and load_balance ?