cfq-iosched: make io priorities inherit CPU scheduling class as well …

…as nice We currently set all processes to the best-effort scheduling class, regardless of what CPU scheduling class they belong to. Improve that so that we correctly track idle and rt scheduling classes as well. Signed-off-by: Jens Axboe <[email protected]>
josf · May 7, 2008 · 6d63c27 · 6d63c27
1 parent dbaf2c0
commit 6d63c27
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Showing 2 changed files with 16 additions and 2 deletions.
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
@@ -1303,10 +1303,10 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
 		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
+		 * no prio set, inherit CPU scheduling settings
 		 */
 		cfqq->ioprio = task_nice_ioprio(tsk);
-		cfqq->ioprio_class = IOPRIO_CLASS_BE;
+		cfqq->ioprio_class = task_nice_ioclass(tsk);
 		break;
 	case IOPRIO_CLASS_RT:
 		cfqq->ioprio = task_ioprio(ioc);

diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
@@ -67,6 +67,20 @@ static inline int task_nice_ioprio(struct task_struct *task)
 	return (task_nice(task) + 20) / 5;
 }
 
+/*
+ * This is for the case where the task hasn't asked for a specific IO class.
+ * Check for idle and rt task process, and return appropriate IO class.
+ */
+static inline int task_nice_ioclass(struct task_struct *task)
+{
+	if (task->policy == SCHED_IDLE)
+		return IOPRIO_CLASS_IDLE;
+	else if (task->policy == SCHED_FIFO || task->policy == SCHED_RR)
+		return IOPRIO_CLASS_RT;
+	else
+		return IOPRIO_CLASS_BE;
+}
+
 /*
  * For inheritance, return the highest of the two given priorities
  */