From: Glauber Costa <firstname.lastname@example.org> To: Paul Turner <email@example.com> Cc: Tejun Heo <firstname.lastname@example.org>, Peter Zijlstra <email@example.com>, <firstname.lastname@example.org>, <email@example.com>, <firstname.lastname@example.org>, <email@example.com>, <firstname.lastname@example.org>, <email@example.com>, <firstname.lastname@example.org>, Dhaval Giani <email@example.com>, Frederic Weisbecker <firstname.lastname@example.org> Subject: Re: [RFC 0/5] forced comounts for cgroups. Date: Fri, 7 Sep 2012 02:36:36 +0400 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <CAPM31RKVYpkc0oTJKjsdsvqBfif=Bovi3a6TE8qdOOpEYOC0Lw@mail.gmail.com> On 09/07/2012 01:11 AM, Paul Turner wrote: > On Thu, Sep 6, 2012 at 1:46 PM, Tejun Heo <firstname.lastname@example.org> wrote: >> Hello, >> >> cc'ing Dhaval and Frederic. They were interested in the subject >> before and Dhaval was pretty vocal about cpuacct having a separate >> hierarchy (or at least granularity). > > Really? Time just has _not_ borne out this use-case. I'll let Dhaval > make a case for this but he should expect violent objection. > I strongly advise against physical violence. In case it is really necessary, please break his legs only. >> On Wed, Sep 05, 2012 at 12:04:47PM +0200, Peter Zijlstra wrote: >>>> cpuacct is rather unique tho. I think it's gonna be silly whether the >>>> hierarchy is unified or not. >>>> >>>> 1. If they always can live on the exact same hierarchy, there's no >>>> point in having the two separate. Just merge them. >>>> >>>> 2. If they need differing levels of granularity, they either need to >>>> do it completely separately as they do now or have some form of >>>> dynamic optimization if absolutely necesary. >>>> >>>> So, I think that choice is rather separate from other issues. If >>>> cpuacct is gonna be kept, I'd just keep it separate and warn that it >>>> incurs extra overhead for the current users if for nothing else. >>>> Otherwise, kill it or merge it into cpu. >>> >>> Quite, hence my 'proposal' to remove cpuacct. >>> >>> There was some whining last time Glauber proposed this, but the one >>> whining never convinced and has gone away from Linux, so lets just do >>> this. >>> >>> Lets make cpuacct print a deprecated msg to dmesg for a few releases and >>> make cpu do all this. >> >> I like it. Currently cpuacct is the only problematic one in this >> regard (cpuset to a much lesser extent) and it would be great to make >> it go away. >> >> Dhaval, Frederic, Paul, if you guys object, please voice your >> opinions. >> >>> The co-mounting stuff would have been nice for cpusets as well, knowing >>> all your tasks are affine to a subset of cpus allows for a few >>> optimizations (smaller cpumask iterations), but I guess we'll have to do >>> that dynamically, we'll just have to see how ugly that is. >> >> Forced co-mounting sounds rather silly to me. If the two are always >> gonna be co-mounted, why not just merge them and switch the >> functionality depending on configuration? I'm fairly sure the code >> would be simpler that way. > > It would be simpler but the problem is we'd break any userspace that > was just doing mount cpuacct? > > Further, even if it were mounting both, userspace code still has to be > changed to read from "cpu.export" instead of "cpuacct.export". > Only if we remove cpuacct. What we can do, and I thought about doing, is just merging cpuacct functionality into cpu. Then we move cpuacct to default no. It will be there for userspace if they absolutely want to use it. > I think a sane path on this front is: > > Immediately: > Don't allow cpuacct and cpu to be co-mounted on separate hierarchies > simultaneously. > that is precisely what my patch does, except it is a bit more generic. > That is: > mount none /dev/cgroup/cpuacct -t cgroupfs -o cpuacct : still works > mount none /dev/cgroup/cpu -t cgroupfs -o cpu : still works > mount none /dev/cgroup/cpux -t cgroupfs -o cpuacct,cpu : still works > > But the combination: > mount none /dev/cgroup/cpu -t cgroupfs -o cpu : still works > mount none /dev/cgroup/cpuacct -t cgroupfs -o cpu : EINVAL [or vice versa]. > > Also: > WARN_ON when mounting cpuacct without cpu, strongly explaining that > ANY such configuration is deprecated. > > Glauber's patchset goes most of the way towards enabling this. > yes. > In a release or two: > Make the restriction strict; don't allow individual mounting of > cpuacct, force it to be mounted ONLY with cpu. > > Glauber's patchset gives us this. > > Finally: > Mirror the interfaces to cpu, print nasty syslog messages about ANY > mounts of cpuacct > Follow that up by eventually removing cpuacct completely > Why don't start with mirroring? It gives more time for people to start switching to it.
next prev parent reply other threads:[~2012-09-06 22:40 UTC|newest] Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-09-04 14:18 Glauber Costa 2012-09-04 14:18 ` [RFC 1/5] cgroup: allow some comounts to be forced Glauber Costa 2012-09-04 14:18 ` [RFC 2/5] sched: adjust exec_clock to use it as cpu usage metric Glauber Costa 2012-09-04 14:18 ` [RFC 3/5] sched: do not call cpuacct_charge when cpu and cpuacct are comounted Glauber Costa 2012-09-04 14:18 ` [RFC 4/5] cpuacct: do not gather cpuacct statistics when not mounted Glauber Costa 2012-09-04 14:18 ` [RFC 5/5] sched: add cpusets to comounts list Glauber Costa 2012-09-04 21:46 ` [RFC 0/5] forced comounts for cgroups Tejun Heo 2012-09-05 8:03 ` Glauber Costa 2012-09-05 8:14 ` Tejun Heo 2012-09-05 8:17 ` Glauber Costa 2012-09-05 8:29 ` Tejun Heo 2012-09-05 8:35 ` Glauber Costa 2012-09-05 8:47 ` Tejun Heo 2012-09-05 8:55 ` Glauber Costa 2012-09-05 9:07 ` Tejun Heo 2012-09-05 9:06 ` Glauber Costa 2012-09-05 9:14 ` Tejun Heo 2012-09-05 9:06 ` Peter Zijlstra 2012-09-05 9:07 ` Peter Zijlstra 2012-09-05 9:22 ` Tejun Heo 2012-09-05 9:11 ` Tejun Heo 2012-09-05 9:12 ` Glauber Costa 2012-09-05 9:19 ` Tejun Heo 2012-09-05 9:30 ` Glauber Costa 2012-09-05 9:26 ` Peter Zijlstra 2012-09-05 9:31 ` Glauber Costa 2012-09-05 9:45 ` Tejun Heo 2012-09-05 9:48 ` Glauber Costa 2012-09-05 9:56 ` Tejun Heo 2012-09-05 10:20 ` Peter Zijlstra 2012-09-06 20:38 ` Tejun Heo 2012-09-06 22:39 ` Glauber Costa 2012-09-06 22:45 ` Tejun Heo 2012-09-05 9:32 ` Tejun Heo 2012-09-05 10:04 ` Peter Zijlstra 2012-09-06 20:46 ` Tejun Heo 2012-09-06 21:11 ` Paul Turner 2012-09-06 22:36 ` Glauber Costa [this message] 2012-09-08 13:36 ` Dhaval Giani
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