linux-kernel - Re: [PATCH v7 01/13] tools/libperf: introduce notion of static polled file descriptors

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Date:   Mon, 15 Jun 2020 17:37:53 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 01/13] tools/libperf: introduce notion of static polled
 file descriptors


On 15.06.2020 15:30, Jiri Olsa wrote:
> On Mon, Jun 15, 2020 at 08:20:38AM +0300, Alexey Budankov wrote:
>>
>> On 08.06.2020 19:07, Jiri Olsa wrote:
>>> On Mon, Jun 08, 2020 at 12:54:31PM +0300, Alexey Budankov wrote:
>>>>
>>>> On 08.06.2020 11:43, Jiri Olsa wrote:
>>>>> On Mon, Jun 08, 2020 at 11:08:56AM +0300, Alexey Budankov wrote:
>>>>>>
>>>>>> On 05.06.2020 19:15, Alexey Budankov wrote:
>>>>>>>
>>>>>>> On 05.06.2020 14:38, Jiri Olsa wrote:
>> <SNIP>
>>>>>>> revents = fdarray_fixed_revents(array, pos);
>>>>>>> fdarray__del(array, pos);
>>>>>>
>>>>>> So how is it about just adding _revents() and _del() for fixed fds with
>>>>>> correction of retval to bool for fdarray__add()?
>>>>>
>>>>> I don't like the separation for fixed and non-fixed fds,
>>>>> why can't we make generic?
>>>>
>>>> Usage models are different but they want still to be parts of the same class
>>>> for atomic poll(). The distinction is filterable vs. not filterable.
>>>> The distinction should be somehow provided in API. Options are:
>>>> 1. expose separate API calls like __add_nonfilterable(), __del_nonfilterable();
>>>>    use nonfilterable quality in __filter() and __poll() and, perhaps, other internals;
>>>> 2. extend fdarray__add(, nonfilterable) with the nonfilterable quality
>>>>    use the type in __filter() and __poll() and, perhaps, other internals;
>>>>    expose less API calls in comparison with option 1
>>>>
>>>> Exposure of pos for filterable fds should be converted to bool since currently
>>>> the returned pos can become stale and there is no way in API to check its state.
>>>> So it could look like this:
>>>>
>>>> fdkey = fdarray__add(array, fd, events, type)
>>>> type: filterable, nonfilterable, somthing else
>>>> revents = fdarray__get_revents(fdkey);
>>>> fdarray__del(array, fdkey);
>>>
>>> I think there's solution without having filterable type,
>>> I'm not sure why you think this is needed
>>>
>>> I'm busy with other things this week, but I think I can
>>> come up with some patch early next week if needed
>>
>> Friendly reminder.
> 
> hm? I believe we discussed this in here:
>   https://lore.kernel.org/lkml/20200609145611.GI1558310@krava/

Do you want it to be implemented like in the patch posted by the link?

~Alexey

> 
> jirka
>