From: Andy Lutomirski <luto@amacapital.net>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Randy Dunlap <rdunlap@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Djalal Harouni <tixxdz@gmail.com>,
Alexey Gladkov <gladkov.alexey@gmail.com>
Subject: Re: [PATCH 1/2 v2] fdmap(2)
Date: Sun, 24 Sep 2017 14:31:23 -0700 [thread overview]
Message-ID: <CALCETrWWUuzF7HaQAS2rf69KcqBrB9epvQPPgKEoK4MNbdVmEw@mail.gmail.com> (raw)
In-Reply-To: <20170924200620.GA24368@avx2>
On Sun, Sep 24, 2017 at 1:06 PM, Alexey Dobriyan <adobriyan@gmail.com> wrote:
> From: Aliaksandr Patseyenak <Aliaksandr_Patseyenak1@epam.com>
>
> Implement system call for bulk retrieveing of opened descriptors
> in binary form.
>
> Some daemons could use it to reliably close file descriptors
> before starting. Currently they close everything upto some number
> which formally is not reliable. Other natural users are lsof(1) and CRIU
> (although lsof does so much in /proc that the effect is thoroughly buried).
>
> /proc, the only way to learn anything about file descriptors may not be
> available. There is unavoidable overhead associated with instantiating
> 3 dentries and 3 inodes and converting integers to strings and back.
>
> Benchmark:
>
> N=1<<22 times
> 4 opened descriptors (0, 1, 2, 3)
> opendir+readdir+closedir /proc/self/fd vs fdmap
>
> /proc 8.31 ą 0.37%
> fdmap 0.32 ą 0.72%
This doesn't have the semantic problem that pidmap does, but I still
wonder why this can't be accomplished by adding a new file in /proc.
next prev parent reply other threads:[~2017-09-24 21:31 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-24 20:06 [PATCH 1/2 v2] fdmap(2) Alexey Dobriyan
2017-09-24 20:08 ` [PATCH v2 2/2] pidmap(2) Alexey Dobriyan
2017-09-24 21:27 ` Andy Lutomirski
2017-09-26 18:46 ` Alexey Dobriyan
2017-09-27 15:04 ` Andy Lutomirski
2017-09-25 7:43 ` Michael Kerrisk (man-pages)
2017-09-25 10:47 ` Djalal Harouni
2017-09-26 5:44 ` kbuild test robot
2017-09-24 21:31 ` Andy Lutomirski [this message]
2017-09-26 18:43 ` [PATCH 1/2 v2] fdmap(2) Alexey Dobriyan
2017-09-25 7:42 ` Michael Kerrisk (man-pages)
2017-09-26 19:00 ` Alexey Dobriyan
2017-09-27 15:03 ` Andy Lutomirski
2017-09-28 7:26 ` Michael Kerrisk (man-pages)
2017-09-28 10:55 ` Alexey Dobriyan
2017-09-28 15:02 ` Andy Lutomirski
2017-10-11 17:37 ` Alexey Dobriyan
2017-09-28 10:10 ` Alexey Dobriyan
2017-10-23 9:29 ` Pavel Machek
2017-10-25 12:45 ` Alexey Dobriyan
2017-10-25 13:48 ` Pavel Machek
2017-09-26 4:25 ` kbuild test robot
2017-10-10 22:08 ` [1/2,v2] fdmap(2) Andrei Vagin
2017-10-11 18:12 ` Alexey Dobriyan
2017-10-12 8:06 ` Andrei Vagin
2017-10-18 11:35 ` Alexey Dobriyan
2017-10-18 17:47 ` Andy Lutomirski
2017-10-19 15:34 ` Alexey Dobriyan
2017-10-20 7:48 ` Greg KH
2017-10-25 13:11 ` Alexey Dobriyan
2017-10-26 7:53 ` Andy Lutomirski
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