Messages in this thread | | | Date | Tue, 28 Apr 2009 11:38:33 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags |
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* KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
> > > > * Pekka Enberg <penberg@cs.helsinki.fi> wrote: > > > > > I have no idea how expensive tracepoints are but I suspect they > > > don't make too much sense for this particular scenario. After all, > > > kmemtrace is mainly interested in _allocation patterns_ whereas > > > this patch seems to be more interested in "memory layout" type of > > > things. > > > > My point is that the allocation patterns can be derived from dynamic > > events. We can build a map of everything if we know all the events > > that led up to it. Doing: > > > > echo 3 > /proc/sys/vm/drop_caches > > > > will clear 99% of the memory allocations, so we can build a new map > > from scratch just about anytime. (and if boot allocations are > > interesting they can be traced too) > > > > _And_ via this angle we'll also have access to the dynamic events, > > in a different 'view' of the same tracepoints - which is obviously > > very useful for different purposes. > > I am one of most strongly want guys to MM tracepoint. but No, many > cunstomer never permit to use drop_caches.
See my other mail i just sent: it would be a natural extension of tracing to also dump all current object state when tracing is turned on. That way no drop_caches is needed at all.
But it has to be expressed in one framework that cares about the totality of the kernel - not just these splintered bits of instrumentation and pieces of statistics.
Ingo
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