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

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Date:	Wed, 25 May 2011 16:11:15 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc:	huang ying <huang.ying.caritas@...il.com>,
	Huang Ying <ying.huang@...el.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()


* Hidetoshi Seto <seto.hidetoshi@...fujitsu.com> wrote:

> (2011/05/22 19:00), Ingo Molnar wrote:
> > * huang ying <huang.ying.caritas@...il.com> wrote:
> >> How to do hardware error recovering in your perf framework?  IMHO, it can be 
> >> something as follow:
> >>
> >> - NMI handler run for the hardware error, where hardware error
> >> information is collected and put into a ring buffer, an irq_work is
> >> triggered for further work
> >> - In irq_work handler, memory_failure_queue() is called to do the real
> >> recovering work for recoverable memory error in ring buffer.
> >>
> >> What's your idea about hardware error recovering in perf?
> > 
> > The first step, the whole irq_work and ring buffer already looks largely 
> > duplicated: you can collect into a perf event ring-buffer from NMI context like 
> > the regular perf events do.
> > 
> > The generalization that *would* make sense is not at the irq_work level really, 
> > instead we could generalize a 'struct event' for kernel internal producers and 
> > consumers of events that have no explicit PMU connection.
> > 
> > This new 'struct event' would be slimmer and would only contain the fields and 
> > features that generic event consumers and producers need. Tracing events could 
> > be updated to use these kinds of slimmer events.
> > 
> > It would still plug nicely into existing event ABIs, would work with event 
> > filters, etc. so the tooling side would remain focused and unified.
> > 
> > Something like that. It is rather clear by now that splitting out irq_work was 
> > a mistake. But mistakes can be fixed and some really nice code could come out 
> > of it! Would you be interested in looking into this?
> 
> Err...?
> 
> Then is it better to write some nice code and throw away the following patch?

No, i think your patch is already a pretty nice simplification of the 
MCE code - using irq_work is obviously better than the open-coded MCE 
vector approach!

These are exactly the kind of small steps towards generalizations 
that i wanted to see: each step without being intrusive and breaking 
stuff and working towards improving the status quo.

Thanks,

	Ingo
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