Re: [PATCH 3/4] RAS: Add a Corrected Errors Collector

["Luck, Tony" <tony.luck@intel.com>]

On Thu, Mar 09, 2017 at 11:08:17AM +0100, Borislav Petkov wrote:
> +config RAS_CEC
> +	bool "Correctable Errors Collector"
> +	depends on X86_MCE && MEMORY_FAILURE && DEBUG_FS
> +	---help---
> +	  This is a small cache which collects correctable memory errors per 4K
> +	  page PFN and counts their repeated occurrence. Once the counter for a
> +	  PFN overflows, we try to soft-offline that page as we take it to mean
> +	  that it has reached a relatively high error count and would probably
> +	  be best if we don't use it anymore.

You added "count_threshold" for me ... so the condition isn't quite "overflows"
like it was in the early versions.

We may need to give some thought on what to do if the attempt to offline
the page fails (e.g. because the page belongs to the kernel). Right now
you delete it from the list, but we will see more errors as the page is
still in use. Eventually the counter will hit count_threshold and we will
try to offline again. Rinse, repeat.

Someone also recently sent me a log from a machine with corrected errors
in over 9000 unique addresses. Need a parameter to allocate more than one
page for the collector, or a way to grow the space.

-Tony