linux-kernel - Re: [PATCH] NR_OPEN should be raised a litle bit

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Message-ID: <473EB138.80603@cosmosbay.com>
Date:	Sat, 17 Nov 2007 10:15:36 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] NR_OPEN should be raised a litle bit

Alan Cox a écrit :
> On Fri, 16 Nov 2007 22:53:08 +0100
> Eric Dumazet <dada1@...mosbay.com> wrote:
> 
>> Time has come to change NR_OPEN value, some production servers hit the
>> not so 'ridiculously high value' of 1024*1024 file descriptors per process.
> 
> Why fiddle with the kernel defaults when every distribution can manage
> this in user space - including picking defaults by memory size or
> platform ?

Please note I am not speaking about the standard 1024 filedescriptors limit, 
but the hardcoded 1024*1024 one.

Tell me more how a user space can overcome this limit ?


Dynamically patching kernel text ?

static struct fdtable * alloc_fdtable(unsigned int nr)
{
...
         nr /= (1024 / sizeof(struct file *));
         nr = roundup_pow_of_two(nr + 1);
         nr *= (1024 / sizeof(struct file *));
         if (nr > NR_OPEN)
                 nr = NR_OPEN;

and :

int expand_files(struct files_struct *files, int nr)
{
         struct fdtable *fdt;

         fdt = files_fdtable(files);
         /* Do we need to expand? */
         if (nr < fdt->max_fds)
                 return 0;
         /* Can we expand? */
         if (nr >= NR_OPEN)
                 return -EMFILE;



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