Re: [PATCH] perf annotate: Remove hist__account_cycles from callback

[Jin, Yao]

On 3/14/2019 10:17 PM, Jin, Yao wrote:
> On 3/14/2019 8:04 PM, Jiri Olsa wrote:
> > On Wed, Mar 13, 2019 at 04:22:54AM +0800, Jin Yao wrote:
> > > The hist__account_cycles is executed when the hist_iter__branch_callback
> > > is called. But it looks it's not necessary. In hist__account_cycles, it
> > > already walks on all branch entries.
> > >
> > > This patch moves the hist__account_cycles out of callback, now the data
> > > processing is much faster than before.
> > >
> > > For example,
> > > perf record -b ...
> > > perf annotate
> > >
> > > The before/after output should be no change.
> >
> > so in the old code it was called multiple times per sample,
> > while after your change it's called just once per sample
> >
> > it increases cycles stats for symbol, so it's strange
> > the behaviour is the same.. could you please exaplin this
> > in more detail?
>
> In __symbol__account_cycles,
> ch[offset].num_aggr++;
> ch[offset].cycles_aggr += cycles;
>
> In annotation__compute_ipc,
> al = notes->offsets[offset];
> al->cycles = ch->cycles_aggr / ch->num_aggr;
>
> So the num_aggr and cycles_aggr are both increased n times, then the 
> final result is the same.

There might be another potential issue in annotation__count_and_fill.

/* Hide data when there are too many overlaps. */
if (ch->reset >= 0x7fff || ch->reset >= ch->num / 2)
	return;

When ch->reset is 0 and ch->num is 1, it returns directly. But for this 
case, the data doesn't need to be hidden since there is no overlap 
happening.

I will post v2 and add this fix.

Thanks
Jin Yao

> > > Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> > > ---
> > > Â tools/perf/builtin-annotate.c | 4 ++--
> > > Â 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/tools/perf/builtin-annotate.c 
> > > b/tools/perf/builtin-annotate.c
> > > index 67f9d9f..77deb3a 100644
> > > --- a/tools/perf/builtin-annotate.c
> > > +++ b/tools/perf/builtin-annotate.c
> > > @@ -159,8 +159,6 @@ static int hist_iter__branch_callback(struct 
> > > hist_entry_iter *iter,
> > > ÂÂÂÂÂ struct perf_evsel *evsel = iter->evsel;
> > > ÂÂÂÂÂ int err;
> > > -ÂÂÂ hist__account_cycles(sample->branch_stack, al, sample, false);
> > > -
> >
> > there's similar code in perf report, could you please cover
> > that as well?
>
> Sure, let me have a try.
>
> Thanks
> Jin Yao
>
> > thanks,
> > jirka
> >
> > > ÂÂÂÂÂ bi = he->branch_info;
> > > ÂÂÂÂÂ err = addr_map_symbol__inc_samples(&bi->from, sample, evsel);
> > > @@ -199,6 +197,8 @@ static int process_branch_callback(struct 
> > > perf_evsel *evsel,
> > > ÂÂÂÂÂ if (a.map != NULL)
> > > ÂÂÂÂÂÂÂÂÂ a.map->dso->hit = 1;
> > > +ÂÂÂ hist__account_cycles(sample->branch_stack, al, sample, false);
> > > +
> > > ÂÂÂÂÂ ret = hist_entry_iter__add(&iter, &a, PERF_MAX_STACK_DEPTH, ann);
> > > ÂÂÂÂÂ return ret;
> > > Â }
> > > --
> > > 2.7.4