Re: Strange IDE performance change in 2.6.1-rc1 (again)

[Valdis . Kletnieks]

On Sat, 03 Jan 2004 04:33:28 +0100, Tobias Diedrich <ranma@xxxxxx>  said:

> Very interesting tidbit:
> 
> with 2.6.1-rc1 and "dd if=/dev/hda of=/dev/null" I get stable 28 MB/s,
> but with "cat < /dev/hda > /dev/null" I get 48 MB/s according to "vmstat
> 5".

'cat' is probably doing a stat() on stdout and seeing it's connected to /dev/null
and not even bothering to do the write() call.  I've seen similar behavior in other
GNU utilities.

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