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Date: Thu, 21 May 2015 16:39:43 -0400 From: Tejun Heo <tj@...nel.org> To: Zefan Li <lizefan@...wei.com> Cc: Peter Zijlstra <peterz@...radead.org>, cgroups@...r.kernel.org, mingo@...hat.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/3] sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem Hello, Li. On Wed, May 20, 2015 at 06:05:37PM +0800, Zefan Li wrote: > > The latency is bound by synchronize_sched_expedited(). Given the way > > cgroups are used in majority of setups (process migration happening > > only during service / session setups), I think this should be okay. > > Actually process migration can happen quite frequently, for example in > Android phones, and that's why Google had an out-of-tree patch to remove > the synchronize_rcu() in that path, which turned out to be buggy. It's still not a very frequent operation tho. We're talking about users switching fore/background jobs here and the expedited synchronization w/ preemption enabled doesn't take much time. In addition, as it currently stands, android is doing memory charge immigration on each fore/background switches. I'm pretty doubtful this would make any difference. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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