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

From: Alexey Budankov <alexey.budankov@linux.intel.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Andi Kleen <ak@linux.intel.com>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 01/13] tools/libperf: introduce notion of static polled file descriptors
Date: Wed, 17 Jun 2020 12:39:56 +0300	[thread overview]
Message-ID: <2818512e-e383-e2be-73ea-92a8b596e593@linux.intel.com> (raw)
In-Reply-To: <20200617092706.GB2210496@krava>


On 17.06.2020 12:27, Jiri Olsa wrote:
> On Mon, Jun 15, 2020 at 06:58:04PM +0200, Jiri Olsa wrote:
>> On Mon, Jun 15, 2020 at 05:37:53PM +0300, Alexey Budankov wrote:
>>>
>>> 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?
>>
>> no idea.. looking for good solution ;-)
> 
> Friendly reminder.

Please see v8: https://lore.kernel.org/lkml/0781a077-aa82-5b4a-273e-c17372a72b93@linux.intel.com/

~Alexey