linux-kernel - Re: [PATCH 1/6] x86-mce: Modify CMCI poll interval to adjust for small check

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Message-ID: <CAFQmdRbmBDQiYxwdhLyo0kg3tZ=9X8t6+Dgabs7ZO1ZvDvekiA@mail.gmail.com>
Date:	Thu, 10 Jul 2014 10:16:56 -0700
From:	Havard Skinnemoen <hskinnemoen@...gle.com>
To:	"Chen, Gong" <gong.chen@...ux.intel.com>
Cc:	Borislav Petkov <bp@...en8.de>, Tony Luck <tony.luck@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ewout van Bekkum <ewout@...gle.com>
Subject: Re: [PATCH 1/6] x86-mce: Modify CMCI poll interval to adjust for
 small check_interval values.

On Thu, Jul 10, 2014 at 2:01 AM, Chen, Gong <gong.chen@...ux.intel.com> wrote:
> On Wed, Jul 09, 2014 at 02:24:31PM -0700, Havard Skinnemoen wrote:
>> On Wed, Jul 9, 2014 at 12:17 PM, Borislav Petkov <bp@...en8.de> wrote:
>> > Why min 3 polls? How do you come up with exactly that frequency?
>>
>> The idea is that if we make it equal to check_interval, it might
>> bounce back and forth a lot. So we need to divide by something, and 8
>> seems like a nice, safe value, and it seems to work well. We're not
>> opposed to considering other values, of course (e.g. 2 and 4 might
>> work well too, but with somewhat higher risk of ping-ponging).
> That value looks chosen a little bit at will. How about updating
> CMCI_POLL_INTERVAL when check_interval is changed to ensure
> CMCI_POLL_INTERVAL <= check_interval always.

I guess that would work equally well, but we still need to determine
the magic number of how much less we want CMCI_POLL_INTERVAL to be.

Havard
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