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Frederic Weisbecker authored
Sometimes we get callchain branches that have a rate under the limit given by the user. Say you launched: perf record -f -g -a ./hackbench 10 perf report -g fractal,10.0 And you got: 2.33% hackbench [kernel] [k] _spin_lock_irqsave | |--78.57%-- remove_wait_queue | poll_freewait | do_sys_poll | sys_poll | sysenter_dispatch | 0xf7ffa430 | 0x1ffadea3c | |--7.14%-- __up_read | up_read | do_page_fault | page_fault | 0xf7ffa430 | 0xa0df710000000a ... It is abnormal to get a 7.14% branch whereas we passed a 10% filter. The problem is that we round down the minimum threshold. This happens mostly when we have very low number of events. If the total amount of your branch is 4 and you have a subranch of 3 events, filtering to 90% will be computed like follows: limit = 4 * 0.9; The result is about 3.6, but the cast to integer will round down to 3. It means that our filter is actually of 75% We must then explicitly round up the minimum threshold. Reported-by:
Ingo Molnar <mingo@elte.hu> Signed-off-by:
Frederic Weisbecker <fweisbec@gmail.com> Cc: acme@redhat.com Cc: peterz@infradead.org Cc: efault@gmx.de LKML-Reference: <20090809024235.GA10146@nowhere> Signed-off-by:
Ingo Molnar <mingo@elte.hu>
c0a8865e