On Thu, 30 Oct, at 11:47:40PM, Peter Zijlstra wrote: > > Let me reply to just this one, I'll do the rest tomorrow, need sleeps. > > On Thu, Oct 30, 2014 at 06:22:36PM -0400, Tejun Heo wrote: > > > > > This controller might not even require the distinction between > > > > configured and effective tho? Can't a new child just inherit the > > > > parent's configuration and never allow the config to become completely > > > > empty? > > > > > > It can do that. But that still has a problem, there is a mapping in > > > hardware which restricts the number of active configurations. The total > > > configuration space is larger than the supported active configurations. > > > > > > So _something_ must fail. The initial proposal was mkdir failing when > > > there were more than the hardware supported active config cgroup > > > directories. The alternative was on-demand activation where we only > > > allocate the hardware resource when the first task gets moved into the > > > group -- which then clearly can fail. > > > > Hmmm... why can't it just refuse creating a different configuration > > when its config space is full? Make children inherit the parent's > > configuration and refuse config writes which require it to create a > > new one if the config space is full. Seems pretty straight-forward. > > What am I missing? > > We could do that I suppose, there is the one corner case that would not > allow, intermediate directories with a restricted config that also have > priv restrictions but no actual tasks. Not sure that makes sense though. Could you elaborate on this configuration?
> Are there any other cases I might have missed? I don't think so. So, for the specific CAT case what you're proposing is make the failure case happen when writing to the cache bitmask file instead of failing mkdir() or echo $tid > tasks ? I think that's OK. If we've run out of CLOS ids I would expect to see -ENOSPC returned, whereas if we try and set an invalid bitmask we'd get -EINVAL. Vikas, Will? -- Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
