Messages in this thread | | | Date | Tue, 31 Jan 2012 17:12:07 +0100 | From | Ingo Molnar <> | Subject | Re: smp: Start up non-boot CPUs asynchronously |
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* Arjan van de Ven <arjan@infradead.org> wrote:
> 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.
I didn't think I'd ever quote Bush, but my reaction to that is: 'Bring it on!' ;-)
Really, we don't want *more* random delays in kernel code.
Thanks,
Ingo
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