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

[Eric Dumazet]

Alan Cox a écrit :
> On Fri, 16 Nov 2007 22:53:08 +0100
> Eric Dumazet <dada1@xxxxxxxxxxxxx> 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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