On 7/7/14, 12:38 PM, Brendan Gregg wrote:
G'Day perf users,
Is there a way to filter perf from tracing itself?
Here's an idle system:
# ./perf record -e syscalls:sys_enter_read -a sleep 5
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.569 MB perf.data (~24864 samples) ]
# ./perf record -e syscalls:sys_enter_write -a sleep 5
[ perf record: Woken up 0 times to write data ]
[ perf record: Captured and wrote 150.381 MB perf.data (~6570251 samples) ]
Note the disparity. perf is capturing its own writes, creating a feedback loop.
Not a filter, but works around the problem using mmap'ed output file:
https://github.com/dsahern/linux/commit/ae2d7010256f5a5b247fb4df9f764a911a34a2f3
David
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