Messages in this thread | | | Date | Wed, 1 Aug 2012 09:14:22 +0200 (CEST) | From | Thomas Gleixner <> | Subject | RE: [PATCH 1/1] kthread: disable preemption during complete() |
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On Thu, 26 Jul 2012, Peter Boonstoppel wrote:
> > > tglx has patches that make the kthread create/destroy stuff from hotplug > > > go away.. that seems like the better approach. > > > Right. That cpu hotplug setup/teardown stuff is ugly. > > If that stuff gets removed complete that's great. The only change I'm aware of right now is the workqueue one: http://thread.gmane.org/gmane.linux.kernel/1329164 > > > > The main thing is avoiding the wakeup preemption from the complete() > > > because we're going to sleep right after anyway. > > You are very likely to be preempted by the complete(), since the newly created thread has a relatively high vruntime. > > > > The comment doesn't really make that clear. > > > Right, the comment is crap. It has nothing to do with kthread_bind() > > and stuff. The whole purpose is to avoid the pointless preemption > > after wakeup. > > The only case I want to solve is the kthread_bind()->wait_task_inactive() scenario. On our platforms this patch reduces average cpu_up() time from about 9ms to 8ms, but max time goes down from 37ms to 8.5ms. cpu_up() latency becomes much more predictable. >
There is a bunch of patches in the queue, which kills the full setup/teardown of per cpu threads and puts those threads into a "park" position instead.
Thanks,
tglx
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