linux-kernel - Re: [PATCH 5/9] HWPoison: add memory_failure

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Date:	Tue, 24 May 2011 10:10:30 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	huang ying <huang.ying.caritas@...il.com>,
	Len Brown <lenb@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	"Wu, Fengguang" <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 5/9] HWPoison: add memory_failure_queue()

On 05/23/2011 07:01 PM, Ingo Molnar wrote:
>> If my understanding as above is correct, I think this is a general and 
>> complex solution.  It is a little hard for user to understand which 'active 
>> filters' are in effect.  He may need some runtime assistant to understand the 
>> code (maybe /sys/events/active_filters, which list all filters in effect 
>> now), because that is hard only by reading the source code.  Anyway, this is 
>> a design style choice.
> 
> I don't think it's complex: the built-in rules are in plain sight (can be in 
> the source code or can even be explicitly registered callbacks), the 
> configuration/tooling installed rules will be as complex as the admin or tool 
> wants them to be.
> 
>> There are still some issues, I don't know how to solve in above framework.
>>
>> - If there are two processes request the same type of hardware error
>>   events.  One hardware error event will be copied to two ring buffers (each 
>>   for one process), but the 'active filters' should be run only once for each 
>>   hardware error event.
> 
> With persistent events 'active filters' should only be attached to the central 
> persistent event.

OK. I see.

>> - How to deal with ring-buffer overflow?  For example, there is full of 
>>   corrected memory error in ring-buffer, and now a recoverable memory error 
>>   occurs but it can not be put into perf ring buffer because of ring-buffer 
>>   overflow, how to deal with the recoverable memory error?
> 
> The solution is to make it large enough. With *every* queueing solution there 
> will be some sort of queue size limit.

Another solution could be:

Create two ring-buffer. One is for logging and will be read by RAS
daemon; the other is for recovering, the event record will be removed
from the ring-buffer after all 'active filters' have been run on it.
Even RAS daemon being restarted or hang, recoverable error can be taken
cared of.

Best Regards,
Huang Ying
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