Messages in this thread | | | Subject | Re: [PATCH v4 2/6] perf record: Get the first sample time and last sample time | From | "Jin, Yao" <> | Date | Fri, 20 Oct 2017 06:49:10 +0800 |
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On 10/20/2017 4:25 AM, Arnaldo Carvalho de Melo wrote: > Em Thu, Oct 19, 2017 at 05:21:27PM -0300, Arnaldo Carvalho de Melo escreveu: >> Em Tue, Oct 03, 2017 at 10:22:34PM +0800, Jin Yao escreveu: >>> In perf record, it's walked on all samples yet. So it's very easy to get >> >> You're saying that perf record walks all samples always? That only >> happens when we generate the build-id table, right? And people disable >> that to speed up the process, knowing that some limitations will come >> from that, for doing analysis right after running it is mostly OK to >> disable the build-id processing. > > So either you add a new option that processes all events without doing > build-id processing (and all the locking, struct thread, map, etc > processing it entails) and just looks at the sample->time, and when > build id processing is enabled, just do as you're doing in this patch, > then, at perf report --time you should look to see if those start/end > times were filled in and if not tell that to the user, i.e. that > either --record-time-boundaries (or a better name :-) ) has to be used, > or, that build-id process, with a short explanation that > --record-time-boundaries is a bit cheaper. > > - Arnaldo >
Hi Arnaldo,
Thanks so much for reminding me that the walking only happens when build-id processing is enabled. Yes, the step is same as what you said so there will be an issue when the build-id processing is disabled.
According to your suggestion, I will provide a new option "--record-time-boundaries" in perf record. If user disables the build-id processing, the perf record will ask user to set the "--record-time-boundaries". If user enables the build-id processing, the perf record will not ask user to set the "--record-time-boundaries".
Also in perf report, if it doesn't see start/end time filled in the perf file header, it will show some information to let user know he should set "--record-time-boundaries" or enable the build-id processing in perf record.
I will provide v5 patch series, maybe some days later.
Thanks Jin Yao
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