Re: [Patch] shm bug introduced with pagecache in 2.3.11

Manfred (manfreds@colorfullife.com)
Sat, 13 Nov 1999 09:48:58 +0100

From: Alan Cox <alan@lxorguk.ukuu.org.uk>
> > You've lost:
>
> > Computer: K6-200, 128 MB Ram, Symbios 810 scsi controller, Fujitsu
> > Magneto-Optical drive, 620 MB [I have no empty scsi disc left :(],
>
> So you benchmarked with a very slow I/O device. Ok that should mean its
> silly numbers for both tied entirely to the seek rate of the media
>
Yes, intentionally, that was the slowest disk I found:
Linux single-threads the pageing-io, ie it cannot reorder the read
operations.
I wrote that this is a huge disadvantage, and the numbers show that.

> > 620,000,000 bytes test file, fat filesystem, the same disk is used for
> > NT and Linux.
>
> Linux FAT performance is slow. Try NTFS (or FAT) versus ext2. That would
> be interesting.
I'll try it with a faster disk, but initial tests show that :
- NT gets faster if I add further threads
- Linux cannot reorder the disk io, and it remains at the same performance
for 1 thread and for 64 threads.
- the benchmark is io bound, ie the internal efficiency of the os doesn't
matter.

Jeff Garzik wrote:
> Is this test done on kernel 2.3.28?
2.3.27

--
    Manfred








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