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

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Date:	Tue, 24 May 2011 04:48:48 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Huang Ying <ying.huang@...el.com>
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()


* Huang Ying <ying.huang@...el.com> wrote:

> >> - 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.

Well, filters will always be executed since they execute when the event is 
inserted - not when it's extracted.

So if you worry about losing *filter* executions (and dependent policy action) 
- there should be no loss there, ever.

But yes, the scheme you outline would work as well: a counting-only event with 
a filter specified - this will do no buffering at all.

So ... to get the ball rolling in this area one of you guys active in RAS 
should really try a first approximation for the active filter approach: add a 
test-TRACE_EVENT() for the errors you are interested in and define a convenient 
way to register policy action with post-filter events. This should work even 
without having the 'active' portion defined at the ABI and filter-string level.

Thanks,

	Ingo
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