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

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

[FabF]

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Andrew,

	Here's a patch to add the asio maxthinktime to sysfs.
Could you apply ?

Regards,
Fabian

[-- Attachment #2: maxthinktime1.diff --]
[-- Type: text/x-patch, Size: 1936 bytes --]

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 00:02:59.000000000 +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,

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

[Andrew Morton]

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?

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

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

[Andrew Morton]

FabF <Fabian.Frederick@skynet.be> wrote:
>
>        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 ;)

Fair enough.  Interesting result.

Can you describe and/or publish ffbench?

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

[FabF]

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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 --]
[-- Type: text/plain, Size: 905 bytes --]

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

[-- Attachment #3: maxthinktime2.diff --]
[-- Type: text/x-patch, Size: 2116 bytes --]

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,

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

[Nick Piggin]

FabF wrote:
> On Sat, 2004-05-01 at 00:42, Andrew Morton wrote:

>>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 ?
> 

No no, writing end user documentation is much easier than writing
kernel code!

But either way you needn't worry about it because this isn't something
that you would want to tweak from userspace really. If you find it
useful to do some tuning then I guess it can go in -mm.

> PS:Attached the patch v2.
> 
> Best regards,
> Fabian
> 
> 
> ------------------------------------------------------------------------
> 
> 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
...

maxthinktime of 5 is below the default antic_expire of 6. This
basically turns off the thinktime heuristic, so it isn't really
surprising that it runs like crap.

The *minimum* maxthinktime you should be playing with is probably
about double the antic_expire value.

Raising the value will make the heuristic a bit more restrictive
which could be a good idea. I think OSDL's STP has a couple of
database tests where the anticipatory scheduler has a small
regression (dbt2, dbt3). They might be helpful to you.