linux-kernel - Re: [PATCH] Allow a larger buffer for writes to cpuset files

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Message-Id: <20061030200053.f9836cce.pj@sgi.com>
Date:	Mon, 30 Oct 2006 20:00:53 -0800
From:	Paul Jackson <pj@....com>
To:	"Paul Menage" <menage@...gle.com>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Allow a larger buffer for writes to cpuset files

Paul M wrote:
> @@ -1292,7 +1292,7 @@ static ssize_t cpuset_common_file_write(
>  	int retval = 0;
> 
>  	/* Crude upper limit on largest legitimate cpulist user might write. */
> -	if (nbytes > 100 + 6 * NR_CPUS)
> +	if (nbytes >= PAGE_SIZE)

On a system with 4 Kbyte pages, this imposes a tighter limit
if NR_CPUS is > 666.

On a system with 16 Kbyte pages, this imposes a tighter limit
if NR_CPUS is > 2714.

Those CPU counts don't look that futuristic to me.

And it makes the limit more aribitrary ... like what the heck does
that check have to do with PAGE_SIZE ?

How about coding for the possibility that either NR_CPUS or MAX_NUMNODES
is larger, and removing 'cpu' from the comment:

	/* Crude upper limit on largest legitimate list user might write. */
	if (nbytes > 100 + 6 * max(NR_CPUS, MAX_NUMNODES))

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@....com> 1.925.600.0401
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