linux-kernel - Re: [PATCH 1/2] perf: Add closing sibling events' file descriptors

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Date:   Tue, 11 Aug 2020 11:03:34 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        "alexey.budankov@...ux.intel.com" <alexey.budankov@...ux.intel.com>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>
Subject: Re: [PATCH 1/2] perf: Add closing sibling events' file descriptors

On Tue, Aug 11, 2020 at 02:47:03PM +0000, David Laight wrote:
> From: Andi Kleen
> > On Mon, Aug 10, 2020 at 10:36:32PM +0200, Peter Zijlstra wrote:
> > > On Mon, Aug 10, 2020 at 07:45:18AM -0700, Andi Kleen wrote:
> > >
> > > > Unfortunately we're kind of stuck with the old NFILE=1024 default
> > > > even though it makes little sense on modern servers.
> > >
> > > Why can't that be changed? It seems to me all of userspace changes all
> > > the time; heck that system-doofus thing flushed 20+ years of sysadmin
> > > experience down the drain, just cause. Why can't we up a file limit?
> > 
> > We could try, but I believe it's hard coded in various places outside
> > the kernel.
> 
> The place it really bites is select().
> Although the kernel supports large bitmaps glibc doesn't.
> The random bit overwrites are a PITA to debug.

Good point.

I remember I asked for a simple define to increase like glibc5 had, but 
they still didn't implement that.

-Andi