Re: Security question: "Text file busy" overwriting executables but not shared libraries?

From: Linus Torvalds (
Date: Sat Oct 13 2001 - 17:19:16 EST

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()".


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This archive was generated by hypermail 2b29 : Mon Oct 15 2001 - 21:00:52 EST