Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-28 13:51:44 +00:00
Code Issues Packages Projects Releases Wiki Activity

perf intel-pt: Fix instructions sampling rate

Browse Source 
The timestamp used to determine if an instruction sample is made, is an
estimate based on the number of instructions since the last known
timestamp. A consequence is that it might go backwards, which results in
extra samples. Change it so that a sample is only made when the
timestamp goes forwards.

Note this does not affect a sampling period of 0 or sampling periods
specified as a count of instructions.

Example:

 Before:

 $ perf script --itrace=i10us
 ls 13812 [003] 2167315.222583:       3270 instructions:u:      7fac71e2e494 __GI___tunables_init+0xf4 (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222667:      30902 instructions:u:      7fac71e2da0f _dl_cache_libcmp+0x2f (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222667:         10 instructions:u:      7fac71e2d9ff _dl_cache_libcmp+0x1f (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222667:          8 instructions:u:      7fac71e2d9ea _dl_cache_libcmp+0xa (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222667:         14 instructions:u:      7fac71e2d9ea _dl_cache_libcmp+0xa (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222667:          6 instructions:u:      7fac71e2d9ff _dl_cache_libcmp+0x1f (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222667:         14 instructions:u:      7fac71e2d9ff _dl_cache_libcmp+0x1f (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222667:          4 instructions:u:      7fac71e2dab2 _dl_cache_libcmp+0xd2 (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222728:      16423 instructions:u:      7fac71e2477a _dl_map_object_deps+0x1ba (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222734:      12731 instructions:u:      7fac71e27938 _dl_name_match_p+0x68 (/lib/x86_64-linux-gnu/ld-2.28.so)
 ...

 After:
 $ perf script --itrace=i10us
 ls 13812 [003] 2167315.222583:       3270 instructions:u:      7fac71e2e494 __GI___tunables_init+0xf4 (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222667:      30902 instructions:u:      7fac71e2da0f _dl_cache_libcmp+0x2f (/lib/x86_64-linux-gnu/ld-2.28.so)
 ls 13812 [003] 2167315.222728:      16479 instructions:u:      7fac71e2477a _dl_map_object_deps+0x1ba (/lib/x86_64-linux-gnu/ld-2.28.so)
 ...

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org
Fixes: f4aa081949 ("perf tools: Add Intel PT decoder")
Link: http://lkml.kernel.org/r/20190510124143.27054-2-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Adrian Hunter 2019-05-10 15:41:41 +03:00 committed by Arnaldo Carvalho de Melo
parent 6466ec14aa
commit 7ba8fa20e2
1 changed files with 10 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
View File

@ -888,16 +888,20 @@ static uint64_t intel_pt_next_period(struct intel_pt_decoder *decoder)
timestamp = decoder->timestamp + decoder->timestamp_insn_cnt;
masked_timestamp = timestamp & decoder->period_mask;
if (decoder->continuous_period) {
if (masked_timestamp != decoder->last_masked_timestamp)
if (masked_timestamp > decoder->last_masked_timestamp)
return 1;
} else {
timestamp += 1;
masked_timestamp = timestamp & decoder->period_mask;
if (masked_timestamp != decoder->last_masked_timestamp) {
if (masked_timestamp > decoder->last_masked_timestamp) {
decoder->last_masked_timestamp = masked_timestamp;
decoder->continuous_period = true;
}
}
if (masked_timestamp < decoder->last_masked_timestamp)
return decoder->period_ticks;
return decoder->period_ticks - (timestamp - masked_timestamp);
}
@ -926,7 +930,10 @@ static void intel_pt_sample_insn(struct intel_pt_decoder *decoder)
case INTEL_PT_PERIOD_TICKS:
timestamp = decoder->timestamp + decoder->timestamp_insn_cnt;
masked_timestamp = timestamp & decoder->period_mask;
decoder->last_masked_timestamp = masked_timestamp;
if (masked_timestamp > decoder->last_masked_timestamp)
decoder->last_masked_timestamp = masked_timestamp;
else
decoder->last_masked_timestamp += decoder->period_ticks;
break;
case INTEL_PT_PERIOD_NONE:
case INTEL_PT_PERIOD_MTC: