Re: [PATCH 5/9] HWPoison: add memory_failure_queue()

From: Ingo Molnar <mingo@elte.hu>
To: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: huang ying <huang.ying.caritas@gmail.com>,
	Huang Ying <ying.huang@intel.com>, Len Brown <lenb@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Andi Kleen <andi@firstfloor.org>,
	"Luck, Tony" <tony.luck@intel.com>,
	"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
	Andi Kleen <ak@linux.intel.com>,
	"Wu, Fengguang" <fengguang.wu@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH 5/9] HWPoison: add memory_failure_queue()
Date: Wed, 25 May 2011 16:11:15 +0200	[thread overview]
Message-ID: <20110525141115.GE19118@elte.hu> (raw)
In-Reply-To: <4DDCB294.9000405@jp.fujitsu.com>

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

> (2011/05/22 19:00), Ingo Molnar wrote:
> > * huang ying <huang.ying.caritas@gmail.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