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SubjectRe: [PATCH 4/5] perf record: mmap output file - v5
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.


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