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

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Date:   Mon, 22 Jun 2020 12:21:42 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.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 Mon, Jun 22, 2020 at 12:47:19PM +0300, Alexey Budankov wrote:

SNIP

> >>>>>> 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 ;-)
> > 
> > how about switching completely to epoll? I tried and it
> > does not look that bad
> 
> Well, epoll() is perhaps possible but why does it want switching to epoll()?
> What are the benefits and/or specific task being solved by this switch? 

epoll change fixes the same issues as the patch you took in v8

on top of it it's not a hack and wil make polling more user
friendly because of the clear interface

> 
> > 
> > there might be some loose ends (interface change), but
> > I think this would solve our problems with fdarray
> 
> Your first patch accomodated in v8 actually avoids fds typing
> and solves pos (=fdarray__add()) staleness issue with fdarray.

yea, it was a change meant for discussion (which never happened),
and I considered it to be more a hack than a solution

I suppose we can live with that for a while, but I'd like to
have clean solution for polling as well

jirka