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Date: Sat, 13 Oct 2001 15:19:16 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: Jamie Lokier <lk@tantalophile.demon.co.uk>
cc: "Eric W. Biederman" <ebiederm@xmission.com>,
        <linux-kernel@vger.kernel.org>
Subject: Re: Security question: "Text file busy" overwriting executables but
 not shared libraries?
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On Sat, 13 Oct 2001, Jamie Lokier wrote:
>
> There are applications (GCC comes to mind) which are using mmap() to
> read files now because it is measurably faster than read(), for
> sufficiently large source files.
>
> I don't know where the optimal costs lie.

The gcc people tested it, and their cut-off point is at 30kB or so.
Anything smaller than that is faster to just "read()".

Now, that's a traditional mmap(), though, which has more overhead than a
"read-with-PAGE_COPY" would have. The pure mmap() approach has the actual
page fault overhead too, along with having to do "fstat()" and "munmap()".

		Linus

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