Re: [PATCH 2.6.6-rc3-mm1] Add maxthinktime to sysfs

FabF
2004-04-30T23:31:43Z

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On Sat, 2004-05-01 at 00:42, Andrew Morton wrote:
> FabF <Fabian.Frederick@skynet.be> wrote:
> >
> > Here's a patch to add the asio maxthinktime to sysfs.
>
> Why? Have you measured any benefit from varying it, and if so, what was
> the result?

Andrew,

I notice huge variations in first seconds of a 10 client
throughput activity as attached (5,100,300 as maxthinktime).
It's just another parameter I'd like to play with ;)
Maybe this one's exposition is not important intrinsequely but we could
bring interesting combinations later ...

>
> Badari, did you find any need to vary this in the AS tuning work which you
> were doing? (What happened to that, btw?)
>
> If we're going to expose this tunable to users it needs to be documented in
> as-iosched.txt

I'm an absolute beginner Andrew ... Maybe someone more experienced could do that ?

PS:Attached the patch v2.

Best regards,
Fabian

[-- Attachment #2: ffbench11.txt --]
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ffbench 11 - Fabian Frederick 04/2004 - asio - maxthinktime - 10 clients
5 100 300
---------------------
5.37 21.26 16.28
11.71 23.10 20.14
15.22 21.05 20.20
13.85 18.03 17.55
11.58 16.39 16.86
11.41 15.50 14.30
11.43 14.37 14.03
11.43 13.82 14.16
11.43 13.60 14.29
11.57 13.27 14.01
11.24 13.06 13.67
10.78 12.91 13.67
10.71 12.41 12.91
10.91 12.53 12.70
10.97 12.32 12.67
10.90 12.34 12.82
10.62 12.25 12.68
10.59 11.81 12.61
10.44 11.40 12.15
10.44 11.35 11.96
10.37 11.36 11.68
10.20 11.19 11.73
10.39 11.18 11.85
10.22 11.22 11.92
10.10 11.15 11.81
10.11 11.03 11.53
9.95 11.00 11.56
10.15 11.21 11.55
10.32 11.17 11.54
10.34 10.96 11.47
10.08 11.02 11.47
10.10 11.14 11.54
10.15 11.14 11.45
10.07 11.04 11.31
10.12 11.08 11.26
10.01 11.04 11.28
10.02 10.93 11.15
9.98 10.70 10.93
9.94 10.60 10.93
9.85 10.45 10.78
9.87 10.40 10.68
9.98 10.37 10.62
9.95 10.28 10.56
9.87 10.20 10.51
9.72 10.16 10.55

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diff -Naur orig/drivers/block/as-iosched.c edited/drivers/block/as-iosched.c
--- orig/drivers/block/as-iosched.c 2004-04-30 20:10:43.000000000 +0200
+++ edited/drivers/block/as-iosched.c 2004-05-01 01:00:36.000000000 +0200
@@ -65,7 +65,7 @@
* or doing a lengthy computation. A small penalty can be justified there, and
* will still catch out those processes that constantly have large thinktimes.
*/
-#define MAX_THINKTIME (HZ/50UL)
+unsigned long maxthinktime=(HZ/50UL);

/* Bits in as_io_context.state */
enum as_io_states {
@@ -869,7 +869,7 @@
if (test_bit(AS_TASK_IORUNNING, &aic->state)
&& in_flight == 0) {
thinktime = jiffies - aic->last_end_request;
- thinktime = min(thinktime, MAX_THINKTIME-1);
+ thinktime = min(thinktime, maxthinktime-1);
} else
thinktime = 0;
as_update_thinktime(ad, aic, thinktime);
@@ -1951,6 +1951,7 @@
{ \
return as_var_show(__VAR, (page)); \
}
+SHOW_FUNCTION(as_maxthinktime_show, maxthinktime);
SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[REQ_SYNC]);
SHOW_FUNCTION(as_writeexpire_show, ad->fifo_expire[REQ_ASYNC]);
SHOW_FUNCTION(as_anticexpire_show, ad->antic_expire);
@@ -1968,6 +1969,7 @@
*(__PTR) = (MAX); \
return ret; \
}
+STORE_FUNCTION(as_maxthinktime_store, &maxthinktime, 0, LONG_MAX);
STORE_FUNCTION(as_readexpire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX);
STORE_FUNCTION(as_writeexpire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX);
STORE_FUNCTION(as_anticexpire_store, &ad->antic_expire, 0, INT_MAX);
@@ -1977,6 +1979,11 @@
&ad->batch_expire[REQ_ASYNC], 0, INT_MAX);
#undef STORE_FUNCTION

+static struct as_fs_entry as_maxthinktime = {
+ .attr = {.name = "maxthinktime", .mode = S_IRUGO | S_IWUSR },
+ .show = as_maxthinktime_show,
+ .store = as_maxthinktime_store,
+};
static struct as_fs_entry as_est_entry = {
.attr = {.name = "est_time", .mode = S_IRUGO },
.show = as_est_show,
@@ -2008,6 +2015,7 @@
};

static struct attribute *default_attrs[] = {
+ &as_maxthinktime.attr,
&as_est_entry.attr,
&as_readexpire_entry.attr,
&as_writeexpire_entry.attr,