linux-kernel - Re: [RFC Patch 0/2] mm: Add parameters to make kernel behavior at memory error on dirty cache selectable

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Date:	Wed, 17 Apr 2013 13:49:46 +0800
From:	Simon Jeons <simon.jeons@...il.com>
To:	Mitsuhiro Tanino <mitsuhiro.tanino.gm@...achi.com>
CC:	Ric Mason <ric.masonn@...il.com>, Andi Kleen <andi@...stfloor.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC Patch 0/2] mm: Add parameters to make kernel behavior at
 memory error on dirty cache selectable

Hi Mitsuhiro,
On 04/12/2013 09:43 PM, Mitsuhiro Tanino wrote:
> (2013/04/11 22:00), Ric Mason wrote:
>> Hi Mitsuhiro,
>> On 04/11/2013 08:51 PM, Mitsuhiro Tanino wrote:
>>> (2013/04/11 12:53), Simon Jeons wrote:
>>>> One question against mce instead of the patchset. ;-)
>>>>
>>>> When check memory is bad? Before memory access? Is there a process scan it period?
>>> Hi Simon-san,
>>>
>>> Yes, there is a process to scan memory periodically.
>>>
>>> At Intel Nehalem-EX and CPUs after Nehalem-EX generation, MCA recovery
>>> is supported. MCA recovery provides error detection and isolation
>>> features to work together with OS.
>>> One of the MCA Recovery features is Memory Scrubbing. It periodically
>>> checks memory in the background of OS.
>> Memory Scrubbing is a kernel thread? Where is the codes of memory scrubbing?
> Hi Ric,
>
> No. One of the MCA Recovery features is Memory Scrubbing.

Memory Scrubbing is a process in CPU?

> And Memory Scrubbing is a hardware feature of Intel CPU.
>
> OS has a hwpoison feature which is included at mm/memory-failure.c.
> A main function is memory_failure().
>
> If Memory Scrubbing finds a memory error, MCA recovery notifies SRAO error
> into OS and OS handles the SRAO error using hwpoison function.
>
>
>>> If Memory Scrubbing find an uncorrectable error on a memory before
>>> OS accesses the memory bit, MCA recovery notifies SRAO error into OS
>> It maybe can't find memory error timely since it is sleeping when memory error occur, can this case happened?
> Memory Scrubbing seems to be operated periodically but I don't have
> information about how oftern it is executed.

If Memory Scurbbing doesn't catch memory error timely, who will send 
SRAR into OS?

>
> Regards,
> Mitsuhiro Tanino
>
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