Re: [PATCH] Linux Kernel Markers 0.5 for Linux 2.6.17 (with probe management)

[Mathieu Desnoyers <compudj@krystal.dyndns.org>]

* 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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