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From(Linus Torvalds)
SubjectRe: File System Performance
DateMon, 12 Nov 2001 21:48:28 +0000 (UTC)
In article <3BF04289.8FC8B7B7@zip.com.au>,
Andrew Morton  <akpm@zip.com.au> wrote:
>
>It's tar.  It cheats.  It somehow detects that the
>output is /dev/null, and so it doesn't read the input files.

Probably the kernel.

If you do a mmap()+write(), the write() to /dev/null won't even read the
mmap contents, which in turn will cause the pages to never be brought
in.

Anything which uses mmap+write will show this.

		Linus
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