linux-kernel - RE: [PATCH] x86: auto poll/interrupt mode switch for CMC to stop CMC storm

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F192F37C0@ORSMSX104.amr.corp.intel.com>
Date:	Thu, 24 May 2012 16:27:49 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Chen Gong <gong.chen@...ux.intel.com>,
	"bp@...64.org" <bp@...64.org>, "x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: RE: [PATCH] x86: auto poll/interrupt mode switch for CMC to stop
 CMC storm

> So can you please explain how this is better than having this strict
> per cpu and avoid all the mess which comes with that patch? The
> approach of letting global state be modified in a random manner is
> just doomed.

Well doomed sounds bad :-) ... and I think I now agree that we should
get rid of global state and have polling vs. CMCI mode be per-cpu. It
means that it will take fractionally longer to react to a storm, but
on the plus side we'll naturally set storm mode on just the cpus
that are seeing it on a multi-socket system without having to check
topology data ... which should be better for the case where a noisy
source of CMCI is plaguing one socket, while other sockets have some
much lower rate of CMCI that we'd still like to log.

Thanks for the review.

-Tony
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