Messages in this thread | | | Date | Thu, 1 Jul 2021 11:26:39 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v8 10/22] perf record: Introduce --threads=<spec> command line option |
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Em Thu, Jul 01, 2021 at 02:50:40PM +0300, Bayduraev, Alexey V escreveu: > On 30.06.2021 21:54, Bayduraev, Alexey V wrote: > > On 30.06.2021 20:28, Arnaldo Carvalho de Melo wrote: > >> I thought you would start with plain:
> >> -j N
> >> And start one thread per CPU in 'perf record' existing CPU affinity > >> mask, then go on introducing more sophisticated modes.
> > As I remember the first prototype [1] and > > [2] https://lore.kernel.org/lkml/20180913125450.21342-1-jolsa@kernel.org/
> > introduces:
> > --thread=mode|number_of_threads
> > where mode defines cpu masks (cpu/numa/socket/etc)
> > Then somewhere while discussing this patchset it was decided, for unification, > > that --thread should only define CPU/affinity masks or their aliases. > > I think Alexei or Jiri could clarify this more.
> >> Have you done this way because its how VTune has evolved over the years > >> and now expects from 'perf record'?
> > VTune uses only --thread=cpu or no threading.
> However we would like to have such sophisticated cpu/affinity masks to > tune perf-record for different workloads.
I don't have, a priori, anything against the modes you propose, as you have a justification for them, its just how we should introduce that.
I.e. first doing the simple case of '-j NCPUS' and then doing what you need, so that we get more granular patches.
Not adding too much complexity per patch pays off when/if we find bugs and need to bisect.
> For example, some HPC workloads prefer "numa" mask or most of telecom > workloads disallow to use cpus where their non-preemtable > communication threads work.
- Arnaldo
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