linux-kernel - Re: [PATCH v8 01/13] tools/libperf: avoid moving of fds at fdarray_

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Date:   Mon, 29 Jun 2020 21:17:00 +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 v8 01/13] tools/libperf: avoid moving of fds at
 fdarray__filter() call

On Mon, Jun 29, 2020 at 06:11:52PM +0300, Alexey Budankov wrote:

SNIP

> >>
> >> I'm confused, are you talking about file descriptors limit now?
> >> this wont be affected by epoll change.. what do I miss?
> > 
> > Currently there is already uname -n limit on the amount of open file descriptors
> > and Perf tool process is affected by that limit.
> > 
> > Moving to epoll() will impose one more max_user_watches limit and that can additionally
> > confine Perf applicability even though default value on some machines currently
> > is high enough.
> 
> Prior making v9 I would prefer to agree on some design to be implemented in order to
> avoid guessing and redundant reiterating.
> 
> Options that I see as good balanced ones are 1) or 5), + non screwing of fds to fix
> staleness of pos(=fdarray__add()).
> 
> Are there any thoughts so far?

let's try it and discuss over the code

jirka