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

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Date:   Tue, 11 Aug 2020 14:47:03 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Andi Kleen' <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
CC:     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

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.

	David

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