Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 15 Apr 2015 11:36:17 -0500 | From | "Serge E. Hallyn" <> | Subject | Re: [PATCH V2] cpuset: Add knob to make allowed masks hotplug invariant on legacy hierarchy |
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On Wed, Apr 15, 2015 at 12:18:11PM -0400, Tejun Heo wrote: > On Wed, Apr 15, 2015 at 11:15:35AM -0500, Serge E. Hallyn wrote: > > The reason would be because it breaks "legacy" software. So that > > would only matter if Preeti needs to run such software. > > Sure, I get that argument but this is changing how the contorller > behaves in a major way.
It is. My main counter to that would be that it is how cpusets should always have worked :)
> There are specifics which may make this > particular case more justifiable but overall the combination of > arguments is pretty weird.
And becomes harder to reason about and review/maintain. I agree there.
From userspace, I suppose one approach (though note it is racy) to solving this would be to have udev rules which
. On cpu unplug, record all cgroups which were using that cpu . on cpu plug, re-add the cpu to all recorded cgroups for that cpu (if any), as well as to any cgroups marked (in some /etc file) as using "all" or a percentage of all cpus.
-serge
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