From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [RFC 0/5] forced comounts for cgroups. Date: Wed, 5 Sep 2012 13:31:56 +0400 Message-ID: <50471C0C.7050600@parallels.com> References: <1346768300-10282-1-git-send-email-glommer@parallels.com> <20120904214602.GA9092@dhcp-172-17-108-109.mtv.corp.google.com> <5047074D.1030104@parallels.com> <20120905081439.GC3195@dhcp-172-17-108-109.mtv.corp.google.com> <50470A87.1040701@parallels.com> <20120905082947.GD3195@dhcp-172-17-108-109.mtv.corp.google.com> <50470EBF.9070109@parallels.com> <20120905084740.GE3195@dhcp-172-17-108-109.mtv.corp.google.com> <1346835993.2600.9.camel@twins> <20120905091140.GH3195@dhcp-172-17-108-109.mtv.corp.google.com> <50471782.6060800@parallels.com> <1346837209.2600.14.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1346837209.2600.14.camel@twins> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Peter Zijlstra Cc: Tejun Heo , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, davej-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, ben-/+tVBieCtBitmTQ+vhA3Yw@public.gmane.org, pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, lennart-mdGvqq1h2p+GdvJs77BJ7Q@public.gmane.org, kay.sievers-tD+1rO4QERM@public.gmane.org On 09/05/2012 01:26 PM, Peter Zijlstra wrote: > On Wed, 2012-09-05 at 13:12 +0400, Glauber Costa wrote: >> On 09/05/2012 01:11 PM, Tejun Heo wrote: >>> Hello, Peter. >>> >>> On Wed, Sep 05, 2012 at 11:06:33AM +0200, Peter Zijlstra wrote: >>>> *confused* I always thought that was exactly what you meant with unified >>>> hierarchy. >>> >>> No, I never counted out differing granularity. >>> >> >> Can you elaborate on which interface do you envision to make it work? >> They will clearly be mounted in the same hierarchy, or as said >> alternatively, comounted. >> >> If you can turn them on/off on a per-subtree basis, which interface >> exactly do you propose for that? > > I wouldn't, screw that. That would result in the exact same problem > we're trying to fix. I want a single hierarchy walk, that's expensive > enough. > >> Would a pair of cgroup core files like available_controllers and >> current_controllers are a lot of drivers do, suffice? > > No.. its not a 'feature' I care to support for 'my' controllers. > > I simply don't want to have to do two (or more) hierarchy walks for > accounting on every schedule event, all that pointer chasing is stupidly > expensive. > You wouldn't have to do more than one hierarchy walks for that. What Tejun seems to want, is the ability to not have a particular controller at some point in the tree. But if they exist, they are always together.