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SubjectRe: [PATCH v3 0/7] perf: Stream comparison
On Mon, Apr 20, 2020 at 09:04:44AM +0800, Jin Yao wrote:

SNIP

> compute_flag div.c:25 compute_flag div.c:25
> compute_flag div.c:22 compute_flag div.c:22
> main div.c:40 main div.c:40
> main div.c:40 main div.c:40
> main div.c:39 main div.c:39*
>
> [ Hot chains in old perf data only ]
>
> hot chain 1:
> cycles: 2, hits: 4.08%
> --------------------------
> main div.c:42
> compute_flag div.c:28
>
> [ Hot chains in new perf data only ]
>
> hot chain 1:
> cycles: 36, hits: 3.36%
> --------------------------
> __random_r random_r.c:357
> __random random.c:293
> __random random.c:293
> __random random.c:291
> __random random.c:291
> __random random.c:291
> __random random.c:288
> rand rand.c:27
> rand rand.c:26
> rand@plt
> rand@plt
> compute_flag div.c:25
> compute_flag div.c:22
> main div.c:40
> main div.c:40
>
> Now we can see, following streams pair is moved to another section
> "[ Hot chains in old perf data but source line changed (*) in new perf data ]"
>
> cycles: 1, hits: 26.80% cycles: 1, hits: 27.30%
> --------------------------- --------------------------
> main div.c:39 main div.c:39*
> main div.c:44 main div.c:44
>


so I tried following:

# ./perf record -e cycles:u -b ./perf bench sched pipe
# ./perf record -e cycles:u -b ./perf bench sched pipe
# ./perf diff -f --stream --before $PWD --after $PWD >out 2>&1

and the out file looks like this:

[ Matched hot chains between old perf data and new perf data ]

[ Hot chains in old perf data but source line changed (*) in new perf data ]

[ Hot chains in old perf data only ]

hot chain 1:
cycles: 0, hits: 4.20%
--------------------------
0xffffffff89c00163

hot chain 2:
cycles: 0, hits: 4.11%
--------------------------
0xffffffff89c00163

hot chain 3:
cycles: 0, hits: 8.22%
--------------------------
0xffffffff89c00163

hot chain 4:
cycles: 0, hits: 5.54%
--------------------------
0xffffffff89c00163

hot chain 5:
cycles: 0, hits: 6.10%
--------------------------
0xffffffff89c00163

[ Hot chains in new perf data only ]

hot chain 1:
cycles: 0, hits: 5.21%
--------------------------
0xffffffff89c00163

hot chain 2:
cycles: 0, hits: 4.79%
--------------------------
0xffffffff89c00163

hot chain 3:
cycles: 0, hits: 5.44%
--------------------------
0xffffffff89c00163

hot chain 4:
cycles: 0, hits: 5.50%
--------------------------
0xffffffff89c00163

hot chain 5:
cycles: 0, hits: 7.14%
--------------------------
0xffffffff89c00163


I'd expected more common paths, from what I can see from 'perf report --branch-history'
on bpth perf.data and perf.data.old

jirka

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