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

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Message-ID: <3B7ECDFA-E6F7-4136-A2E4-6115C5A4791B@fb.com>
Date:   Mon, 4 Mar 2019 19:49:06 +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 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?

> 
>> 
>>> };
>>> 
>>> typedef int (perf_evlist__thread_cb_t)(perf_evlist, union perf_event *event,....)
>> 
>> How do we use this callback? We need a way to specify which
>> events to poll (mmap, bpf_event, ksymbol, etc). How do we do 
>> that with the callback function?
> 
> you provide your own callback

I guess I get your point now. I can try that. 

Thanks,
Song

> jirka