Btrfs: set ioprio of scrub readahead to idle

Reduce ioprio class of scrub readahead threads to idle priority.
This setting is fixed. This priority has shown the best performance
during all measurements.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e176f8c551f7b752352715869797b284e330a4b2..1c665ebe47e052565b66042433564df977f720bd 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -173,6 +173,9 @@ static int btrfs_csum_sizes[] = { 4, 0 };
 #define BTRFS_FT_XATTR         8
 #define BTRFS_FT_MAX           9
 
+/* ioprio of readahead is set to idle */
+#define BTRFS_IOPRIO_READA (IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0))
+
 /*
  * The key defines the order in the tree, and so it also defines (optimal)
  * block layout.

diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index ac5d010858848d007e380d529476ad9eb4f6fb31..48a4882d8ad5955eaa0be2b940e35f0b3b2a7f6f 100644 (file)
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -718,13 +718,18 @@ static void reada_start_machine_worker(struct btrfs_work *work)
 {
        struct reada_machine_work *rmw;
        struct btrfs_fs_info *fs_info;
+       int old_ioprio;
 
        rmw = container_of(work, struct reada_machine_work, work);
        fs_info = rmw->fs_info;
 
        kfree(rmw);
 
+       old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current),
+                                      task_nice_ioprio(current));
+       set_task_ioprio(current, BTRFS_IOPRIO_READA);
        __reada_start_machine(fs_info);
+       set_task_ioprio(current, old_ioprio);
 }
 
 static void __reada_start_machine(struct btrfs_fs_info *fs_info)