linux-kernel - Re: [RESEND][PATCH] mm: vmstats: tlb flush counters

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Date:	Tue, 23 Jul 2013 10:17:27 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Dave Hansen <dave@...1.net>
Cc:	Raghavendra KT <raghavendra.kt.linux@...il.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org, linux-mm@...ck.org,
	Raghavendra KT <raghavendra.kt@...ux.vnet.ibm.com>
Subject: Re: [RESEND][PATCH] mm: vmstats: tlb flush counters


* Dave Hansen <dave@...1.net> wrote:

> On 07/22/2013 03:06 AM, Ingo Molnar wrote:
> > Btw., would be nice to also integrate these VM counters into perf as well, 
> > as an instrumentation variant/option.
> > 
> > It could be done in an almost zero overhead fashion using jump-labels I 
> > think.
> > 
> > [ Just in case someone is bored to death and is looking for an interesting 
> >   side project ;-) ]
> 
> I'd actually been thinking about making them in to tracepoints, but the 
> tracepoint macros seem to create #include messes if you try to use them 
> in very common headers.
> 
> Agree it would be an interesting side project, though. :)

Yes, tracepoints was what I was thinking about, it would allow easy 
integration into perf [and it's useful even without any userspace side] - 
as long as:

 - the tracepoints trace the counts/sums, not just the events themselves
 - when the tracepoints are not active the VM counts are still maintained 
   separately

I.e. the existing VM counts and its extraction facilities are not impacted 
in any way, just a new channel of instrumentation is provided - 
jump-label/static-key optimized by virtue of being tracepoints.

Thanks,

	Ingo
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