Messages in this thread | | | Date | Wed, 2 Oct 2013 18:01:18 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 2/4] nohz: Synchronize sleep time stats with seqlock |
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On Wed, Oct 02, 2013 at 07:35:49AM -0700, Arjan van de Ven wrote: > On 10/2/2013 5:45 AM, Frederic Weisbecker wrote: > >On Tue, Oct 01, 2013 at 06:59:57PM +0200, Peter Zijlstra wrote: > >>On Tue, Oct 01, 2013 at 06:47:10PM +0200, Frederic Weisbecker wrote: > >>>Yeah thinking more about it, the preempt disable was probably not > >>>necessary. Now that's trading 2 atomics + 1 Lock/Unlock with 2 Lock/Unlock. > >> > >>It trades the current 2 atomics for 2 LOCK/UNLOCK. And on x86_64 that's > >>2 atomics. > > > >Do you mean 2 atomics for LOCK/UNLOCK? Or is that pair optimized somehow > >in x86? > > unlock is not actually an atomic. > > and on some modern machines, neither is the lock, for the uncontended case ;-) >
Yeah, we are never getting short on black magic as the time goes :)
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