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Open Source and information security mailing list archives
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Date: Fri, 13 May 2011 09:36:21 -0700 From: Andi Kleen <andi@...stfloor.org> To: James Bottomley <James.Bottomley@...senPartnership.com> Cc: x86@...nel.org, linux-mm <linux-mm@...ck.org>, linux-kernel <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de> Subject: Re: Possible sandybridge livelock issue James Bottomley <James.Bottomley@...senPartnership.com> writes: > > When the hang occurred, kswapd basically pegged one core in 100% system > time. This looks like there's something specific to sandybridge that > causes this type of bad interaction. I was wondering if it could be > something to to with a scheduling problem in turbo mode? Once kswapd > goes flat out, the core its on will kick into turbo mode, which causes > it to get preferentially scheduled there, leading to the live lock. Sounds unlikely to me. Turbo mode does not affect the scheduler and the cores are (reasonably) independent. > The only evidence I have to support this theory is that when I reproduce > the problem with PREEMPT, the core pegs at 100% system time and stays > there even if I turn off the load. However, if I can execute work that > causes kswapd to be kicked off the core it's running on, it will calm > back down and go to sleep. Turbo mode just makes the CPU faster, but it should not change the scheduler decisions. -Andi -- ak@...ux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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