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Re: [PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management)
- From: Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
- To: Ingo Molnar <mingo at elte dot hu>
- Cc: Martin Bligh <mbligh at google dot com>, "Frank Ch. Eigler" <fche at redhat dot com>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, prasanna at in dot ibm dot com, Andrew Morton <akpm at osdl dot org>, Paul Mundt <lethal at linux-sh dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, Jes Sorensen <jes at sgi dot com>, Tom Zanussi <zanussi at us dot ibm dot com>, Richard J Moore <richardj_moore at uk dot ibm dot com>, Michel Dagenais <michel dot dagenais at polymtl dot ca>, Christoph Hellwig <hch at infradead dot org>, Greg Kroah-Hartman <gregkh at suse dot de>, Thomas Gleixner <tglx at linutronix dot de>, William Cohen <wcohen at redhat dot com>, ltt-dev at shafik dot org, systemtap at sources dot redhat dot com, Alan Cox <alan at lxorguk dot ukuu dot org dot uk>
- Date: Fri, 22 Sep 2006 13:28:59 -0400
- Subject: Re: [PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management)
- References: <20060921160009.GA30115@Krystal> <20060921160656.GA24774@elte.hu> <20060921214248.GA10097@Krystal> <20060922064955.GA4167@elte.hu> <20060922140329.GA20839@Krystal> <20060922165352.GA16476@elte.hu> <20060922171156.GA18363@Krystal> <20060922171224.GA18964@elte.hu>
* Ingo Molnar (mingo@elte.hu) wrote:
> >
> > Yes, sorry, my mistake. This kind of fault is not as infrequent as you
> > may think, as every newly allocated vmalloc region will cause vmalloc
> > faults on every processes on the system that are trying to access
> > them. I agree that it should not be a standard event people would be
> > interested in.
>
> most of the vmalloc area that is allocated on a typical system are
> modules - and they get loaded on bootup and rarely unloaded. Even for
> other vmalloc-ed areas like netfilter, the activation of them is during
> bootup. So from that point on the number of vmalloc faults is quite low.
> (zero on most systems) If you still want to trace it i'd suggest a
> separate type of event for it.
Yes, with this typical vmalloc usage pattern in perspective, we completely
agree. We also agree on having a separate kind of event for this, as it requires
the tracer code to be vmalloc-fault-reentrant (very tricky).
Mathieu
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