Messages in this thread | | | Subject | Re: [PATCH v7 2/6] perf record: Get the first sample time and last sample time | From | "Jin, Yao" <> | Date | Fri, 5 Jan 2018 09:15:03 +0800 |
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On 1/5/2018 3:09 AM, Arnaldo Carvalho de Melo wrote: > Em Fri, Dec 08, 2017 at 09:13:42PM +0800, Jin Yao escreveu: >> In the default 'perf record' configuration, all samples are processed, >> to create the HEADER_BUILD_ID table. So it's very easy to get the >> first/last samples and save the time to perf file header via the >> function write_sample_time(). >> >> Later, at post processing time, perf report/script will fetch >> the time from perf file header. > > So, at this point I was expecting that that record would be present on > the perf.data file: > > [acme@jouet perf]$ perf record --timestamp-boundary sleep 1 > Cannot read kernel map > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.001 MB perf.data (7 samples) ] > [acme@jouet perf]$ perf report -D | grep PERF_RECORD_SAMPLE | wc -l > 7 > [acme@jouet perf]$ perf report -D | grep PERF_RECORD_SAMPLE_TIME > [acme@jouet perf]$ > > What am I doing wrong? > > To clarify, this is with just the first two patches in this series > applied. > > - Arnaldo >
Hi Arnaldo,
The timestamp boundary information is saved in perf file header.
So if we want to look at them, we need to add '--header' in perf report.
For example,
root@skl:/tmp# perf report -D --header | grep 'time of' # time of first sample : 248333.706656 # time of last sample : 248357.215328
Thanks Jin Yao
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