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Date: Sat, 13 Mar 2021 10:00:26 +0800
From: Yang Jihong <yangjihong1@...wei.com>
To: Namhyung Kim <namhyung@...nel.org>
CC: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Yao Jin <yao.jin@...ux.intel.com>, <gustavoars@...nel.org>,
<mliska@...e.cz>, linux-kernel <linux-kernel@...r.kernel.org>,
<zhangjinhao2@...wei.com>
Subject: Re: [PATCH] perf annotate: Fix sample events lost in stdio mode
Hello, Namhyung
On 2021/3/12 18:20, Yang Jihong wrote:
> Hello,
>
> On 2021/3/12 16:39, Namhyung Kim wrote:
>> On Fri, Mar 12, 2021 at 4:19 PM Yang Jihong <yangjihong1@...wei.com>
>> wrote:
>>>
>>>
>>> Hello,
>>> On 2021/3/12 13:49, Namhyung Kim wrote:
>>>> Hi,
>>>>
>>>> On Fri, Mar 12, 2021 at 12:24 PM Yang Jihong
>>>> <yangjihong1@...wei.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@...wei.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
>>
>> Yeah, so this is for a symbol.
>>
>>>
>>> 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
>>
>> This should be for each IP (ideally it should be per instruction).
>>
>>>
>>> By bugs, do you mean there's something wrong?
>>
>> No. I think we were saying about different things. :)
>>
> OK, :)
>>
>>>>>> 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(¬es->src->cycles_hist);
>>>>>> - zfree(¬es->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(¬es->src->cycles_hist);
>>> - zfree(¬es->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.
>>
>> I prefer changing the sort order (and removing the zfree and comments).
>>
> OK, I'll submit a v3 patch based on the "changing the sort order" solution.
>
I have submitted the v3 patch, look forward to your review:
https://lore.kernel.org/patchwork/patch/1394619/
> Thanks,
> Yang
>> Thanks,
>> Namhyung
Thanks,
Yang
>> .
>>
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