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From: Eric Dumazet <dada1@cosmosbay.com>
To: Vadim Lobanov <vlobanov@speakeasy.net>
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fdtable: Eradicate fdarray overflow.
Date: Thu, 12 Oct 2006 07:19:20 +0200	[thread overview]
Message-ID: <452DD058.7000301@cosmosbay.com> (raw)
In-Reply-To: <200610111958.03238.vlobanov@speakeasy.net>

Vadim Lobanov a écrit :
> 
> diff -Npru old/fs/file.c new/fs/file.c
> --- old/fs/file.c	2006-10-10 18:58:21.000000000 -0700
> +++ new/fs/file.c	2006-10-11 19:37:23.000000000 -0700
> @@ -164,9 +164,8 @@ static struct fdtable * alloc_fdtable(un
>  	 * the fdarray into page-sized chunks: starting at a quarter of a page,
>  	 * and growing in powers of two from there on.
>  	 */
> -	nr++;
>  	nr /= (PAGE_SIZE / 4 / sizeof(struct file *));
> -	nr = roundup_pow_of_two(nr);
> +	nr = roundup_pow_of_two(nr + 1);
>  	nr *= (PAGE_SIZE / 4 / sizeof(struct file *));
>  	if (nr > NR_OPEN)
>  		nr = NR_OPEN;

Hi Vadim

I find your PAGE_SIZE/4 minimum allocation quite unjustified.

For architectures with 64K PAGE_SIZE, we endup allocating 16K, for poor tasks 
that happen to touch a not so high (>= 64) file descriptor...

I would vote for a fixed size, like 1024

Eric

  reply	other threads:[~2006-10-12  5:19 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-10-12  2:58 Vadim Lobanov
2006-10-12  5:19 ` Eric Dumazet [this message]
2006-10-12  6:07   ` Vadim Lobanov
2006-10-12  6:32     ` Eric Dumazet
2006-10-12  7:16       ` Vadim Lobanov

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