raid5: raid5d handle stripe in batch way

Let raid5d handle stripe in batch way to reduce conf->device_lock locking.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 978ba9b7a3c4d6019ce1a550009e5a4e108ab152..9e41ae37bd40828c6aa9961056d0288d48892ded 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4574,6 +4574,30 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
        return handled;
 }
 
+#define MAX_STRIPE_BATCH 8
+static int handle_active_stripes(struct r5conf *conf)
+{
+       struct stripe_head *batch[MAX_STRIPE_BATCH], *sh;
+       int i, batch_size = 0;
+
+       while (batch_size < MAX_STRIPE_BATCH &&
+                       (sh = __get_priority_stripe(conf)) != NULL)
+               batch[batch_size++] = sh;
+
+       if (batch_size == 0)
+               return batch_size;
+       spin_unlock_irq(&conf->device_lock);
+
+       for (i = 0; i < batch_size; i++)
+               handle_stripe(batch[i]);
+
+       cond_resched();
+
+       spin_lock_irq(&conf->device_lock);
+       for (i = 0; i < batch_size; i++)
+               __release_stripe(conf, batch[i]);
+       return batch_size;
+}
 
 /*
  * This is our raid5 kernel thread.
@@ -4584,7 +4608,6 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
  */
 static void raid5d(struct mddev *mddev)
 {
-       struct stripe_head *sh;
        struct r5conf *conf = mddev->private;
        int handled;
        struct blk_plug plug;
@@ -4598,6 +4621,7 @@ static void raid5d(struct mddev *mddev)
        spin_lock_irq(&conf->device_lock);
        while (1) {
                struct bio *bio;
+               int batch_size;
 
                if (
                    !list_empty(&conf->bitmap_list)) {
@@ -4621,21 +4645,16 @@ static void raid5d(struct mddev *mddev)
                        handled++;
                }
 
-               sh = __get_priority_stripe(conf);
-
-               if (!sh)
+               batch_size = handle_active_stripes(conf);
+               if (!batch_size)
                        break;
-               spin_unlock_irq(&conf->device_lock);
-               
-               handled++;
-               handle_stripe(sh);
-               release_stripe(sh);
-               cond_resched();
+               handled += batch_size;
 
-               if (mddev->flags & ~(1<<MD_CHANGE_PENDING))
+               if (mddev->flags & ~(1<<MD_CHANGE_PENDING)) {
+                       spin_unlock_irq(&conf->device_lock);
                        md_check_recovery(mddev);
-
-               spin_lock_irq(&conf->device_lock);
+                       spin_lock_irq(&conf->device_lock);
+               }
        }
        pr_debug("%d stripes handled\n", handled);