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SubjectRe: [PATCH] perf annotate: Fix sample events lost in stdio mode
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Hello,
On 2021/3/12 13:49, Namhyung Kim wrote:
> Hi,
>
> On Fri, Mar 12, 2021 at 12:24 PM Yang Jihong <yangjihong1@huawei.com> wrote:
>>
>> Hello, Namhyung
>>
>> On 2021/3/11 22:42, Namhyung Kim wrote:
>>> Hi,
>>>
>>> On Thu, Mar 11, 2021 at 5:48 PM Yang Jihong <yangjihong1@huawei.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>> On 2021/3/6 16:28, Yang Jihong wrote:
>>>>> In hist__find_annotations function, since have a hist_entry per IP for the same
>>>>> symbol, we free notes->src to signal already processed this symbol in stdio mode;
>>>>> when annotate, entry will skipped if notes->src is NULL to avoid repeated output.
>>>
>>> I'm not sure it's still true that we have a hist_entry per IP.
>>> Afaik the default sort key is comm,dso,sym which means it should have a single
>>> hist_entry for each symbol. It seems like an old comment..
>>>
>> Emm, yes, we have a hist_entry for per IP.
>> a member named "sym" in struct "hist_entry" points to symbol,
>> different IP may point to the same symbol.
>
> Are you sure about this? It seems like a bug then.
>
Yes, now each IP corresponds to a hist_entry :)

Last week I found that some sample events were missing when perf
annotate in stdio mode, so I went through the annotate code carefully.

The event handling process is as follows:
process_sample_event
evsel_add_sample
hists__add_entry
__hists__add_entry
hists__findnew_entry
hist_entry__new -> here allock new hist_entry

hist_entry__inc_addr_samples
symbol__inc_addr_samples
symbol__hists
annotated_source__new -> here alloc annotate soruce
annotated_source__alloc_histograms -> here alloc histograms

By bugs, do you mean there's something wrong?
>>
>> The hist_entry struct is as follows:
>> struct hist_entry {
>> ...
>> struct map_symbol ms;
>> ...
>> };
>> struct map_symbol {
>> struct maps *maps;
>> struct map *map;
>> struct symbol *sym;
>> };
>>
>>>>>
>>>>> However, there is a problem, for example, run the following command:
>>>>>
>>>>> # perf record -e branch-misses -e branch-instructions -a sleep 1
>>>>>
>>>>> perf.data file contains different types of sample event.
>>>>>
>>>>> If the same IP sample event exists in branch-misses and branch-instructions,
>>>>> this event uses the same symbol. When annotate branch-misses events, notes->src
>>>>> corresponding to this event is set to null, as a result, when annotate
>>>>> branch-instructions events, this event is skipped and no annotate is output.
>>>>>
>>>>> Solution of this patch is to add a u8 member to struct sym_hist and use a bit to
>>>>> indicate whether the symbol has been processed.
>>>>> Because different types of event correspond to different sym_hist, no conflict
>>>>> occurs.
>>>>> ---
>>>>> tools/perf/builtin-annotate.c | 22 ++++++++++++++--------
>>>>> tools/perf/util/annotate.h | 4 ++++
>>>>> 2 files changed, 18 insertions(+), 8 deletions(-)
>>>>>
>>>>> diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
>>>>> index a23ba6bb99b6..c8c67892ae82 100644
>>>>> --- a/tools/perf/builtin-annotate.c
>>>>> +++ b/tools/perf/builtin-annotate.c
>>>>> @@ -372,15 +372,21 @@ static void hists__find_annotations(struct hists *hists,
>>>>> if (next != NULL)
>>>>> nd = next;
>>>>> } else {
>>>>> - hist_entry__tty_annotate(he, evsel, ann);
>>>>> + struct sym_hist *h = annotated_source__histogram(notes->src,
>>>>> + evsel->idx);
>>>>> +
>>>>> + if (h->processed == 0) {
>>>>> + hist_entry__tty_annotate(he, evsel, ann);
>>>>> +
>>>>> + /*
>>>>> + * Since we have a hist_entry per IP for the same
>>>>> + * symbol, set processed flag of evsel in sym_hist
>>>>> + * to signal we already processed this symbol.
>>>>> + */
>>>>> + h->processed = 1;
>>>>> + }
>>>>> +
>>>>> nd = rb_next(nd);
>>>>> - /*
>>>>> - * Since we have a hist_entry per IP for the same
>>>>> - * symbol, free he->ms.sym->src to signal we already
>>>>> - * processed this symbol.
>>>>> - */
>>>>> - zfree(&notes->src->cycles_hist);
>>>>> - zfree(&notes->src);
>>>>> }
>>>>> }
>>>>> }
>>>>> diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h
>>>>> index 096cdaf21b01..89872bfdc958 100644
>>>>> --- a/tools/perf/util/annotate.h
>>>>> +++ b/tools/perf/util/annotate.h
>>>>> @@ -228,6 +228,10 @@ void symbol__calc_percent(struct symbol *sym, struct evsel *evsel);
>>>>> struct sym_hist {
>>>>> u64 nr_samples;
>>>>> u64 period;
>>>>> +
>>>>> + u8 processed : 1, /* whether symbol has been processed, used for annotate */
>>>>> + __reserved : 7;
>>>
>>> I think just a bool member is fine.
>>>
>> OK, I have submitted the v2 patch and changed to bool member, new patch
>> is as follows, look forward to your review:
>> https://lore.kernel.org/patchwork/patch/1393901/
>>
>>>>> +
>>>>> struct sym_hist_entry addr[];
>>>>> };
>>>>>
>>>>>
>>>> Please check whether this solution is feasible, look forward to your review.
>>>
>>> What about this? (not tested)
>>>
>>> diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
>>> index a23ba6bb99b6..a91fe45bd69f 100644
>>> --- a/tools/perf/builtin-annotate.c
>>> +++ b/tools/perf/builtin-annotate.c
>>> @@ -374,13 +374,6 @@ static void hists__find_annotations(struct hists *hists,
>>> } else {
>>> hist_entry__tty_annotate(he, evsel, ann);
>>> nd = rb_next(nd);
>>> - /*
>>> - * Since we have a hist_entry per IP for the same
>>> - * symbol, free he->ms.sym->src to signal we already
>>> - * processed this symbol.
>>> - */
>>> - zfree(&notes->src->cycles_hist);
>>> - zfree(&notes->src);
>>> }
>>> }
>>> }
>>>
>> This solution may have the following problem:
>> For example, if two sample events are in two different processes but in
>> the same symbol, repeated output may occur.
>> Therefore, a flag is required to indicate whether the symbol has been
>> processed to avoid repeated output.
>
> Hmm.. ok. Yeah we don't care about the processes here.
> Then we should remove it from the sort key like below:
>
> @@ -624,6 +617,7 @@ int cmd_annotate(int argc, const char **argv)
> if (setup_sorting(annotate.session->evlist) < 0)
> usage_with_options(annotate_usage, options);
> } else {
> + sort_order = "dso,symbol";
> if (setup_sorting(NULL) < 0)
> usage_with_options(annotate_usage, options);
> }
>
>
Are you referring to this solution?
--- a/tools/perf/builtin-annotate.c
+++ b/tools/perf/builtin-annotate.c
@@ -374,13 +374,6 @@ static void hists__find_annotations(struct hists
*hists,
} else {
hist_entry__tty_annotate(he, evsel, ann);
nd = rb_next(nd);
- /*
- * Since we have a hist_entry per IP for the same
- * symbol, free he->ms.sym->src to signal we already
- * processed this symbol.
- */
- zfree(&notes->src->cycles_hist);
- zfree(&notes->src);
}
}
}
@@ -624,6 +617,7 @@ int cmd_annotate(int argc, const char **argv)
if (setup_sorting(annotate.session->evlist) < 0)
usage_with_options(annotate_usage, options);
} else {
+ sort_order = "dso,symbol";
if (setup_sorting(NULL) < 0)
usage_with_options(annotate_usage, options);
}
It seems to be a better solution without adding new member.
I just tested it and it works.
If we decide to use this solution, I'll resubmit a v3 patch.
> Thanks,
> Namhyung
> .
>
Thanks,
Yang
.

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