Messages in this thread | | | Date | Tue, 31 Jan 2012 07:22:16 -0800 | From | Arjan van de Ven <> | Subject | Re: smp: Start up non-boot CPUs asynchronously |
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On Tue, 31 Jan 2012 15:31:31 +0100 Ingo Molnar <mingo@elte.hu> wrote:
> > > > by inspection, anything that calls > > get_online_cpus()/put_online_cpus() will block while a CPU is > > coming up. This is used in things like kmem_cache_create()... > > which is used about everywhere. (there's various other > > places... more or less it's a requirement for using the > > for_each_online_cpu() api correctly) > > Still magic delays are not acceptable - we want to face any > remaining performance problems head on, we want to understand > and fix them correctly.
it's not really a performance problem as it is an obvious "we have a ton of back-to-back writers on a read-write lock that we have quite a few readers for". Unless the writers back off a little, the readers are going to get starved.
-- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org
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