linux-kernel - Re: [PATCH v4 perf,bpf 14/15] perf: introduce side band thread

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Message-ID: <DB8CAEB3-B02B-41DE-9BBE-55B3C899C806@fb.com>
Date:   Mon, 4 Mar 2019 20:44:25 +0000
From:   Song Liu <songliubraving@...com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     Netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "acme@...hat.com" <acme@...hat.com>,
        "jolsa@...nel.org" <jolsa@...nel.org>,
        "namhyung@...nel.org" <namhyung@...nel.org>
Subject: Re: [PATCH v4 perf,bpf 14/15] perf: introduce side band thread



> On Mar 4, 2019, at 12:41 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> 
> On Mon, Mar 04, 2019 at 07:49:06PM +0000, Song Liu wrote:
>> 
>> 
>>> On Mar 4, 2019, at 5:52 AM, Jiri Olsa <jolsa@...hat.com> wrote:
>>> 
>>> On Wed, Feb 27, 2019 at 05:52:52PM +0000, Song Liu wrote:
>>>> 
>>>> 
>>>>> On Feb 27, 2019, at 5:21 AM, Jiri Olsa <jolsa@...hat.com> wrote:
>>>>> 
>>>>> On Mon, Feb 25, 2019 at 04:20:18PM -0800, Song Liu wrote:
>>>>> 
>>>>> SNIP
>>>>> 
>>>>>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
>>>>>> index 8c902276d4b4..61b87c8111e6 100644
>>>>>> --- a/tools/perf/util/evlist.c
>>>>>> +++ b/tools/perf/util/evlist.c
>>>>>> @@ -19,6 +19,7 @@
>>>>>> #include "debug.h"
>>>>>> #include "units.h"
>>>>>> #include "asm/bug.h"
>>>>>> +#include "bpf-event.h"
>>>>>> #include <signal.h>
>>>>>> #include <unistd.h>
>>>>>> 
>>>>>> @@ -1841,3 +1842,102 @@ struct perf_evsel *perf_evlist__reset_weak_group(struct perf_evlist *evsel_list,
>>>>>> 	}
>>>>>> 	return leader;
>>>>>> }
>>>>>> +
>>>>>> +static struct perf_evlist *sb_evlist;
>>>>>> +pthread_t poll_thread;
>>>>> 
>>>>> so some of the things are static and some like poll_args
>>>>> you alloced on the stack.. I dont like this interface,
>>>>> could we come up with something generic? perhaps
>>>>> encapsulated in perf_evlist, like:
>>>> 
>>>> I picked global sb_evlist and poll_thread because there 
>>>> should be only one sb_evlist and one thread polling it. 
>>>> There might be multiple evsel on the sb_evlist. 
>>>> 
>>>> I am not sure I understand your suggestion..
>>>> 
>>>>> struct perf_evlist {
>>>>> 	...
>>>>> 	struct {
>>>>> 		pthread_t	th;
>>>>> 		int		state;
>>>>> 	} thread;
>>>> 
>>>> This will not be used by the main perf_evlist, right?
>>> 
>>> no, just by the thread interface
>> 
>> What is "state" here?
> 
> it's replacement for the 'done' pointer u had,
> which I did not like.. leting each thread having
> its own state is better IMO
> 
> jirka

I see. Let me try that. 

Song