Re: [PATCH] x86 idle: repair large-server 50-watt idle-powerregression

[Peter Zijlstra]

On Thu, Dec 19, 2013 at 06:25:35PM +0100, Peter Zijlstra wrote:
> On Thu, Dec 19, 2013 at 06:07:41PM +0100, Ingo Molnar wrote:
> > Likewise, having a barrier before the MONITOR looks sensible as well. 
> 
> I again have to disagree, one would expect monitor to flush all that is
> required to start the monitor -- and it actually does so. As is
> testified by this extra CLFLUSH being called a bug workaround.

SDM states that MONITOR is ordered like a LOAD, and a LOAD cannot pass
a previous STORE to the same address.

That said; there's enough holes in there to swim a titanic through,
seeing how MONITOR stares at an entire cacheline and LOAD/STORE order is
specified on location, whatever that means.


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