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authorJin Yao <yao.jin@linux.intel.com>2017-12-08 16:13:41 +0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2018-01-08 17:20:51 +0300
commit6011518db3bd04c80cd3ce3e6aea1c399739adb4 (patch)
tree4e6edf7cd148ae187fd75557778888e24c52cade /tools/perf/util/header.h
parent40c39e3046411f84bab82f66783ff3593e2bcd9b (diff)
downloadlinux-6011518db3bd04c80cd3ce3e6aea1c399739adb4.tar.xz
perf header: Add infrastructure to record first and last sample time
perf report/script/... have a --time option to limit the time range of output. That's very useful to slice large traces, e.g. when processing the output of perf script for some analysis. But right now --time only supports absolute time. Also there is no fast way to get the start/end times of a given trace except for looking at it. This makes it hard to e.g. only decode the first half of the trace, which is useful for parallelization of scripts Another problem is that perf records are variable size and there is no synchronization mechanism. So the only way to find the last sample reliably would be to walk all samples. But we want to avoid that in perf report/... because it is already quite expensive. That is why storing the first sample time and last sample time in perf record is better. This patch creates a new header feature type HEADER_SAMPLE_TIME and related ops. Save the first sample time and the last sample time to the feature section in perf file header. That will be done when, for instance, processing build-ids, where we already have to process all samples to create the build-id table, take advantage of that to further amortize that processing by storing HEADER_SAMPLE_TIME to make 'perf report/script' faster when using --time. Committer testing: After this patch is applied the header is written with zeroes, we need the next patch, for "perf record" to actually write the timestamps: # perf report -D | grep PERF_RECORD_SAMPLE\( 22501155244406 0x44f0 [0x28]: PERF_RECORD_SAMPLE(IP, 0x4001): 25016/25016: 0xffffffffa21be8c5 period: 1 addr: 0 <SNIP> 22501155793625 0x4a30 [0x28]: PERF_RECORD_SAMPLE(IP, 0x4001): 25016/25016: 0xffffffffa21ffd50 period: 2828043 addr: 0 # perf report --header | grep "time of " # time of first sample : 0.000000 # time of last sample : 0.000000 # Changelog: v7: 1. Rebase to latest perf/core branch. 2. Add following clarification in patch description according to Arnaldo's suggestion. "That will be done when, for instance, processing build-ids, where we already have to process all samples to create the build-id table, take advantage of that to further amortize that processing by storing HEADER_SAMPLE_TIME to make 'perf report/script' faster when using --time." v4: Use perf script time style for timestamp printing. Also add with the printing of sample duration. v3: Remove the definitions of first_sample_time/last_sample_time from perf_session. Just define them in perf_evlist Signed-off-by: Jin Yao <yao.jin@linux.intel.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Kan Liang <kan.liang@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1512738826-2628-2-git-send-email-yao.jin@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util/header.h')
-rw-r--r--tools/perf/util/header.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
index 317fb901e47f..f28aaaa3a440 100644
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -35,6 +35,7 @@ enum {
HEADER_AUXTRACE,
HEADER_STAT,
HEADER_CACHE,
+ HEADER_SAMPLE_TIME,
HEADER_LAST_FEATURE,
HEADER_FEAT_BITS = 256,
};