Re: [PATCH 1/6] x86-mce: Modify CMCI poll interval to adjust for small check_interval values.

From: Borislav Petkov
Date: Wed Jul 09 2014 - 15:18:03 EST

On Wed, Jul 09, 2014 at 10:09:21AM -0700, Havard Skinnemoen wrote:
> From: Ewout van Bekkum <ewout@xxxxxxxxxx>
> The CMCI poll interval was updated to pick the minimum interval between
> the original 30 seconds and the check_interval divided by 8 (minimum of
> 3 polls).

Why min 3 polls? How do you come up with exactly that frequency?

> This resolves a bug where the CMCI storm handler is unable to return to
> interrupt mode from polling mode, if the check_interval shorter than the
> CMCI poll interval. This problem is caused by the mce_timer_fn function
> which only allows the poll interval to be incremented up to the
> check_interval, while the mce_intel_adjust_timer function requires the
> poll interval to be greater than the CMCI poll interval before leaving
> the CMCI_STORM_ACTIVE state.

Interesting. So it seems you guys want to set the check_interval to
something < 30 secs.

Out of curiosity, what is your use case which requires such small
check_interval setting?

Maybe we need to redesign and simplify this intervals thing to make it
more user-friendly...

Btw, on a related note, we're working on a small mechanism which
collects correctable errors in the kernel and when a certain count for a
physical error address has been reached, we soft-offline that page. We'd
appreciate it if you guys took a look and told us whether it makes sense
to you:



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