Re: [PATCH][CFT] new IO scheduler for 2.4.20

Con Kolivas
2003-05-30T23:26:11Z

On Sat, 31 May 2003 08:09, Neil Schemenauer wrote:
> The major benefit of this patch is that read latency is much lower while
> lots of writes are occuring. On my machine, running:
>
> while :; do dd if=/dev/zero of=foo bs=1M count=1000 conv=notrunc; done
>
> makes 2.4.20 unusable. With this patch the "write bomb" causes no
> particular problems.
>
> With this version of the patch I've improved the bulk read performance
> of the elevator. The bonnie++ results are now:
>
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP
> 2.4.20 1G 13001 97 34939 18 13034 7 12175 92 34112 14
> 2.4.20-nas 1G 12923 98 36471 17 13340 8 10809 83 35569 13
>
> Note that the "rewrite" and "per-char read" stats are slightly bogus for
> 2.4.20-nas. Reads get a boost in priority over writes. When the
> "per-char read" test has started there is still some writing happening
> from the rewrite test. I think the net effect is that the "rewrite"
> number is too high and the "per-char read" number is too low.
>
> I would be very pleased if someone could run some tests on using bonnie,
> contest, or their other favorite benchmarks and post the results.

Nice to see 2.4 getting some attention. I'll try and get around to contesting
it.

How does this compare to akpm's read-latency2 patch that he posed some time
ago? That seems to make a massive difference but was knocked back for style
or approach.

Con