linux-kernel - Re: [PATCH] x86 idle: repair large-server 50-watt idle-power regression

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Message-ID: <20131219192714.GP16438@laptop.programming.kicks-ass.net>
Date:	Thu, 19 Dec 2013 20:27:14 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Len Brown <lenb@...nel.org>,
	x86@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	stable@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86 idle: repair large-server 50-watt idle-power
 regression

On Thu, Dec 19, 2013 at 11:22:01AM -0800, H. Peter Anvin wrote:
> On 12/19/2013 10:19 AM, Ingo Molnar wrote:
> > 
> > ( It would also be nice to know whether MONITOR loads that cacheline 
> >   into the CPUs cache, and in what state it loads it. )
> > 
> 
> I would assume that is implementation-dependent.  However, one plausible
> implementation is to load the cache line into the cache in shared state
> and monitor for evictions.

I suppose the monitor part is the important part because certain C
states drop all cache, presumably including the cacheline we're actually
monitoring.


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