Am 27.09.2015 um 20:02 schrieb Milian Wolff: > On Freitag, 25. September 2015 20:27:45 CEST martin wrote: >> Hello, >> >> I'm new to Cachegrind (and cache simulation in general). >> >> I'm trying to do a memory trace of my application, but only for >> operations that go to DRAM, that is, only if there was a LLC miss >> should I care. Is it possible to achieve that with Cachegrind? AFAICS, >> it only counts the number of events (and where they happened), but >> maybe it wouldn't be too hard to modify it to print the address every >> time a LLC miss happens. If anyone could point me to the right place >> to look, I would appreciate it. > > You could also use perf for this use case, if your CPU has the required > performance counters. This is also going to be much faster and more accurate, > as you don't need to simulate anything, but get the real counters directly > from hardware: > > perf record --event cache-misses --call-graph dwarf <your application>
Yes, using perf for real measurement is another option if you are fine with sampled results (not every access). This way you get the behavior of the real cache. But if I remember right, it is more tricky to get the data addresses printed out. On Intel something like perf record -d -e cpu/mem-loads,ldlat=100/pp <app> "-d" is writing data addresses into output, "/pp" is requesting PEBS for hardware to provide data addresses in the first place, and "ldlat=100" only counts events with load latency at least 100 cycles, which should be memory accesses. To get the addresses, you could use perf report -D | grep addr There is a field "period" in the output which shows you how many events you lost due to sampling. Theoretically, one can ask for every event via "perf record -c 1 ...", but I suppose there are most events missed due to buffer overrun in the kernel or other effects (at least the machine does not lock up here :-). Josef ------------------------------------------------------------------------------ _______________________________________________ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
