Re: stochastic fair queueing in the elevator [Re: [BENCHMARK] 2.4.20-ck3 / aa / rmap with contest]

From: Andrew Morton (
Date: Mon Feb 10 2003 - 06:21:01 EST

Andrea Arcangeli <> wrote:
> On Mon, Feb 10, 2003 at 09:40:34PM +1100, Nick Piggin wrote:
> > I don't know too much about SCSI stuff, but if driver / wire / device
> > overheads were that much higher at 128K compared to 512K I would
> > think something is broken or maybe optimised badly.
> I guess it's also a matter of the way the harddisk can serve the I/O if
> it sees it all at the same time, not only the cpu/bus protocol after all
> minor overhead. Most certainly it's not a software mistake in linux
> that the big commands runs that much faster. Again go check the numbers
> in bigbox.html between my tree, 2.4 and 2.5 in bonnie read sequential,
> to see the difference between 128k commands and 512k commands with
> reads, these are facts. (and no writes and no seeks here)

I thought scsi in 2.5 was doing 512k I/O's at present???

Doesn't Randy attribute the differences there to an updated
qlogic driver? (Or was the update to allow 512k I/O's? ;))
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