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


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;
_
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