Messages in this thread | | | Date | Wed, 11 Dec 2013 17:44:03 +0100 | From | Peter Zijlstra <> | Subject | Re: 50 Watt idle power regression bisected to Linux-3.10 |
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On Wed, Dec 11, 2013 at 03:42:38PM +0100, Ingo Molnar wrote: > Another thing that is required I think is to issue a write barrier > before CLFLUSH instruction. By my (possibly incorrect ...) reading of > the documentation CLFLUSH does not appear to be ordered (at all), so > it might execute before the modification to the affected memory? > > > So something like: > > if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR)) { > smp_wmb(); /* order CLFLUSH */ > clflush(¤t_thread_info()->flags); > }
smp_wmb() is a NO-OP on x86 remember :-)
Also, a wmb doesn't actually need to flush the store buffers.
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