Re: High read Latency test (Anticipatory I/O scheduler)

[Nick Piggin]

John Chatelle wrote:

>   I haven't seen much duplicated results regarding the Robert Love article 
> in the February 2004 Linux Journal article, also reachable in the hyperlink:
>          http://www.linuxjournal.com/article.php?sid=6931
>
> Although the 1st simple test: "Write starved reads" gets results comparable
> to the results reported in the Article, Our results for the 2nd test: "High 
> Read latency" delivers results opposite our expectations...

Hi John,
Can you try the following patch please? If that doesn't help, can you
show me what /sys/block/hda/queue/iosched/est_time says after your
test has been running for a couple of minutes.

Thanks
Nick

 linux-2.6-npiggin/drivers/block/as-iosched.c |    2 ++
 1 files changed, 2 insertions(+)

diff -puN drivers/block/as-iosched.c~as-exit-prob drivers/block/as-iosched.c
--- linux-2.6/drivers/block/as-iosched.c~as-exit-prob	2004-02-21 09:38:54.000000000 +1100
+++ linux-2.6-npiggin/drivers/block/as-iosched.c	2004-02-21 09:39:22.000000000 +1100
@@ -734,8 +734,10 @@ static int as_can_break_anticipation(str
 	if (aic->ttime_samples == 0) {
 		if (ad->new_ttime_mean > ad->antic_expire)
 			return 1;
+#if 0
 		if (ad->exit_prob > 128)
 			return 1;
+#endif
 	} else if (aic->ttime_mean > ad->antic_expire) {
 		/* the process thinks too much between requests */
 		return 1;

_