Messages in this thread |  | | From | Namhyung Kim <> | Subject | Re: [PATCH 4/5] perf record: mmap output file - v5 | Date | Tue, 19 Nov 2013 11:30:45 +0900 |
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On Mon, 18 Nov 2013 19:17:37 -0700, David Ahern wrote: > On 11/18/13, 7:13 PM, Namhyung Kim wrote: >> I think it should be >> >> perf record -e cycles -F 4000 -e faults -c 1 --call-graph dwarf,8192 -a -- sleep 1 >> >> (at least to generate the feedback spiral more efficiently..) > > you don't need the cycles. faults by itself works. Each event contains > 2 pages of data in the sample. With mmap-based output a single > sample (1 page fault in any process) generates 2-3 page faults by perf > which cause 2-3 >8k samples to be generated, which generates faults, > ....
But after perf touches all pages in ring-buffer and stack, it won't generate page-faults for itself anymore, right?
Hmm.. thinking it again, perf has all ring-buffer pages in memory when mmap() called, right? If so why not doing something like MAP_POPULATE so that it doesn't need to generate minor-faults?
Thanks, Namhyung
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