On 11/18/2010 02:59 PM, Josef Weidendorfer wrote: > With instrumentation on, you still can decide not to aggregate events in given > threads by switching the collection state on/off with > CALLGRIND_TOGGLE_COLLECT. > The collection state is thread specific.
Okay great, that clarifies a lot for me. I just use --collect-atstart=no
and then use CALLGRIND_TOGGLE_COLLECT where needed.
Is specifying --toggle-collect=function the same as putting a toggle at
the entry and exit of that function?
> The big difference between instrumentation and collection state is the
> following:
> if instrumentation is switched off, the state of the cache is not updated.
> Thus,
> after switching instrumentation state on, callgrind starts with a freshly
> initialized
> cache, ie. you will get a lot of cold misses. This would not happen in
> reality, as
How are the misses calculated into the costs of the functions? Will it
make a substantial difference? In the code I'm profiling I'd imagine
under normal use it should be nearing 0% cache misses.
> The option to switch instrumentation mode is only useful for "fast
> forwarding" over
> uninteresting, large parts of the code, where you want all threads to
> progress fast.
The basic reason why I wanted to do this was because I have a couple
threads that aren't of interest but consume the vast majority of CPU
cycles. So when I run valgrind I'll get something like 150M events, only
about 10M of which are of interest. I was trying to get it to go faster.
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