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>

1 files changed, 32 insertions, 13 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 978ba9b7a3c4..9e41ae37bd40 100644
--- 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);