Re: [PATCH] direct-IO API change

[Andrew Morton <akpm@digeo.com>]

Lincoln Dale wrote:
> 
> At 04:23 PM 4/10/2002 -0700, Linus Torvalds wrote:
> >Especially since I thought that O_DIRECT on the regular file (or block
> >device) performed about as well as raw does anyway these days? Or is that
> >just one of my LSD-induced flashbacks?
> 
> from my multiple 64/66 PCI bus + multiple 2gbit/s FC HBA tests, yes,
> they're around the same.
> (now up to 390mbyte/sec throughput on latest & greatest x86 hardware i
> have; front-side-bus no longer the limiting factor, but dual 64/66 PCI).
> 
> of course, purely synthetic tests designed to stress Fibre Channel
> switching infrastructure, not real-world disk i/o..
> 

direct-io has lost its challenge ;)

I'd love to see the result of some pagecache testing on that
setup if you have time.

Nothing fancy - just:

for i in $(each ext2 mountpoint)
do
	dd if=/dev/zero of=$i/foo bs-1M count=4000 &
done
vmstat 1

and

for i in $(each ext2 mountpoint)
do
	cat $i/foo > /dev/null &
done
vmstat 1

Linus's current BK tree has a few warmups which will help the
writeout phase a little.