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author | Frederic Weisbecker <fweisbec@gmail.com> | 2009-08-08 22:19:15 -0400 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2009-08-09 07:07:46 -0400 |
commit | c0a8865e32c8d1a562db38e06ef31ef23282f646 (patch) | |
tree | 8cf7a402e4012998166287135204c201c6a83acd /Documentation/Changes | |
parent | 183f3b0887083d36c8a25cd5e3518906415d1889 (diff) |
perf tools: callchain: Fix bad rounding of minimum rate
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>
Diffstat (limited to 'Documentation/Changes')
0 files changed, 0 insertions, 0 deletions