Messages in this thread |  | | Date | Mon, 18 Nov 2013 17:34:49 -0700 | From | David Ahern <> | Subject | Re: [PATCH 4/5] perf record: mmap output file - v5 |
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On 11/18/13, 5:24 PM, Namhyung Kim wrote: >>>> What now? Can we add the mmap path as an option? >>> >>> I'd say an option is always a possibility, but someone please try >>> what happens if you use stupid large events (dwarf stack copies) on >>> PERF_COUNT_SW_PAGE_FAULTS (.period=1) while recording with mmap(). >>> >>> The other option is to simply disallow PERF_SAMPLE_STACK_USER for >>> that event. >>> >>> Personally I think 8k copies for every event are way stupid anyway, >>> that's a metric ton of data at a huge cost. >> >> Well, with 1 khz sampling of a single threaded workload it's 8MB per >> second - that's 80 MB for 10 seconds profiling - not the end of the >> world. > > We now use 4 khz sampling frequency by default, just FYI. :)
I think Peter is asking about: perf record -e faults -c 1 --call-graph dwarf,8192 -a -- sleep 1
And as expected it is a massive feedback spiraling out of control.
David
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