linux-kernel - Re: [BUG] long freezes on thinkpad t60

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Message-ID: <20070626105602.GD2691@ff.dom.local>
Date:	Tue, 26 Jun 2007 12:56:02 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Eric Dumazet <dada1@...mosbay.com>,
	Chuck Ebbert <cebbert@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Miklos Szeredi <miklos@...redi.hu>, chris@...ee.ca,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	akpm@...ux-foundation.org
Subject: Re: [BUG] long freezes on thinkpad t60

On Tue, Jun 26, 2007 at 06:42:10PM +1000, Nick Piggin wrote:
...
> They should also improve performance in heavily contended case due to
> the nature of how they spin, but I know that's not something you want
> to hear about. And theoretically there should be no reason why xadd is
> any slower than dec and look at the status flags, should there? I never
> implementedit in optimised assembly to test though...
...

BTW, could you explain why the below diagnose doesn't relate
to your solution?

On 06/21/2007 12:08 PM, Ingo Molnar wrote:
...
> So it seems the problem was that if a core kept _truly_ modifying a 
> cacheline via atomics in a high enough frequency, it could artificially 
> starve the other core. (which would keep waiting for the cacheline to be 
> released one day, and which kept the first core from ever making any 
> progress) To me that looks like a real problem on the hardware side - 
> shouldnt cacheline ownership be arbitrated a bit better than that?
> 

Thanks & regards,
Jarek P.
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