Messages in this thread | | | From | Namhyung Kim <> | Date | Thu, 22 Sep 2022 09:32:06 -0700 | Subject | Re: [PATCH 1/2] perf: Use sample_flags for addr |
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Hi Peter,
On Thu, Sep 22, 2022 at 7:48 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Wed, Sep 21, 2022 at 03:00:31PM -0700, Namhyung Kim wrote: > > Use the new sample_flags to indicate whether the addr field is filled by > > the PMU driver. As most PMU drivers pass 0, it can set the flag only if > > it has a non-zero value. And use 0 in perf_sample_output() if it's not > > filled already. > > So no objection to the general idea; just a question > > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > > index 368bdc4f563f..f4a13579b0e8 100644 > > --- a/include/linux/perf_event.h > > +++ b/include/linux/perf_event.h > > @@ -1028,7 +1028,6 @@ struct perf_sample_data { > > * minimize the cachelines touched. > > */ > > u64 sample_flags; > > - u64 addr; > > struct perf_raw_record *raw; > > u64 period; > > > > @@ -1040,6 +1039,7 @@ struct perf_sample_data { > > union perf_sample_weight weight; > > union perf_mem_data_src data_src; > > u64 txn; > > + u64 addr; > > > > u64 type; > > u64 ip; > > Is there a reason you placed the variable where you did?
No I just followed the previous change.
> > I'm thinking we should look at what perf-tool thinks is the common set > of SAMPLE flags and make sure those fields are grouped in as little > cachelines as possible. > > Things like @ip and @type, which are basically *always* set, should > definitely be on top, no?
Yes, you're right. With this change we can move the optional fields and group the common fields on top - like ip, period, pid and so on.
Will send a patch to do the move on top of this, ok?
Thanks, Namhyung
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