2006-05-27 01:50:50

by Con Kolivas

Subject: [patch] cfq: ioprio inherit rt class

Jens, ml

I was wondering if cfq io priorities should be explicitly set to the realtime
class when no io priority is specified from realtime tasks as in the
following patch? (rt_task() will need to be modified to suit the PI changes in
-mm)

---
Set cfq io priority class to realtime and scale the priority according to the
rt priority when no io priority is explicitly set in realtime tasks.

Signed-off-by: Con Kolivas <[email protected]>

---
block/cfq-iosched.c | 4 ++--
include/linux/ioprio.h | 12 +++++++++++-
2 files changed, 13 insertions(+), 3 deletions(-)

Index: linux-2.6.17-rc5-ck2/block/cfq-iosched.c
===================================================================
--- linux-2.6.17-rc5-ck2.orig/block/cfq-iosched.c 2006-05-25 21:32:45.000000000 +1000
+++ linux-2.6.17-rc5-ck2/block/cfq-iosched.c 2006-05-25 23:55:22.000000000 +1000
@@ -1334,10 +1334,10 @@ static void cfq_init_prio_data(struct cf
printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
case IOPRIO_CLASS_NONE:
/*
- * no prio set, place us in the middle of the BE classes
+ * Select class and ioprio according to policy and nice
*/
+ cfqq->ioprio_class = task_policy_ioprio_class(tsk);
cfqq->ioprio = task_nice_ioprio(tsk);
- cfqq->ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_RT:
cfqq->ioprio = task_ioprio(tsk);
Index: linux-2.6.17-rc5-ck2/include/linux/ioprio.h
===================================================================
--- linux-2.6.17-rc5-ck2.orig/include/linux/ioprio.h 2006-05-25 23:02:06.000000000 +1000
+++ linux-2.6.17-rc5-ck2/include/linux/ioprio.h 2006-05-25 23:55:22.000000000 +1000
@@ -22,7 +22,7 @@
* class, the default for any process. IDLE is the idle scheduling class, it
* is only served when no one else is using the disk.
*/
-enum {
+enum ioprio_class {
IOPRIO_CLASS_NONE,
IOPRIO_CLASS_RT,
IOPRIO_CLASS_BE,
@@ -51,8 +51,18 @@ static inline int task_ioprio(struct tas
return IOPRIO_PRIO_DATA(task->ioprio);
}

+static inline enum ioprio_class
+ task_policy_ioprio_class(struct task_struct *task)
+{
+ if (rt_task(task))
+ return IOPRIO_CLASS_RT;
+ return IOPRIO_CLASS_BE;
+}
+
static inline int task_nice_ioprio(struct task_struct *task)
{
+ if (rt_task(task))
+ return (task->rt_priority * IOPRIO_BE_NR / MAX_RT_PRIO);
return (task_nice(task) + 20) / 5;
}


--
-ck

2006-05-27 02:08:42

by Con Kolivas

Subject: Re: [patch] cfq: ioprio inherit rt class

On Saturday 27 May 2006 11:50, Con Kolivas wrote:
> Jens, ml
>
> I was wondering if cfq io priorities should be explicitly set to the
> realtime class when no io priority is specified from realtime tasks as in
> the following patch? (rt_task() will need to be modified to suit the PI
> changes in -mm)
>
> ---
> Set cfq io priority class to realtime and scale the priority according to
> the rt priority when no io priority is explicitly set in realtime tasks.

sorry, rather than this:
> + return (task->rt_priority * IOPRIO_BE_NR / MAX_RT_PRIO);

it should be:
return ((MAX_RT_PRIO - task->rt_priority) * IOPRIO_BE_NR / MAX_RT_PRIO);

--
-ck