On 03/11/2014 06:09 PM, Dongsheng Yang wrote:
As the task nice value is in [-20, 19] and the io priority is in [0, 7],
and the convert method from niceval to ioprio is implemented with an
opened code in task_nice_ioprio().
This patch move the implementation to a macro NICE_TO_IOPRIO, making
it more readable and modular.
Signed-off-by: Dongsheng Yang <yangds.f...@cn.fujitsu.com>
---
include/linux/ioprio.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index beb9ce1..c0faa0b 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -18,6 +18,11 @@
#define ioprio_valid(mask) (IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
/*
+ * Convert the nice value [19,-20] to io priority value [0,7].
+ */
+#define NICE_TO_IOPRIO(nice) (nice_to_rlimit(nice) / 5)
+
Hi Peter,
As you asked, why I added this macro in ioprio.h? And why it is better?
IMO, there is a policy to convert a nice value to io priority, that
divide the nice
range into 8 parts by 5. I think this is a common requirement for lots
of io subsystem.
So I implement this policy with NICE_TO_IOPRIO.
About function task_nice_iopiro(), it is to get the iopriority of a
task. It should get the
nice value at first and then use the NICE_TO_IOPRIO to convert it to
ioprio in the policy.
When our policy changed, we need only update the center controller,
NICE_TO_IOPRIO.
Keep the others work well.
This is my point about this patch. I wish it explained better. Thanx.
+/*
* These are the io priority groups as implemented by CFQ. RT is the realtime
* class, it always gets premium service. BE is the best-effort scheduling
* class, the default for any process. IDLE is the idle scheduling class, it
@@ -52,7 +57,7 @@ enum {
*/
static inline int task_nice_ioprio(struct task_struct *task)
{
- return (task_nice(task) + 20) / 5;
+ return NICE_TO_IOPRIO(task_nice(task));
}
/*
--
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