[patch 08/22] fuse: update backing_dev_info congestion state

[Miklos Szeredi]

From: Miklos Szeredi <mszeredi@xxxxxxx>

Set the read and write congestion state if the request queue is close
to blocking, and clear it when it's not.

This prevents unnecessary blocking in readahead and writeback.

Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---

Index: linux/fs/fuse/dev.c
===================================================================
--- linux.orig/fs/fuse/dev.c	2007-02-27 14:40:55.000000000 +0100
+++ linux/fs/fuse/dev.c	2007-02-27 14:41:09.000000000 +0100
@@ -224,6 +224,10 @@ static void request_end(struct fuse_conn
 			fc->blocked = 0;
 			wake_up_all(&fc->blocked_waitq);
 		}
+		if (fc->num_background == FUSE_CONGESTION_THRESHOLD) {
+			clear_bdi_congested(&fc->bdi, READ);
+			clear_bdi_congested(&fc->bdi, WRITE);
+		}
 		fc->num_background--;
 	}
 	spin_unlock(&fc->lock);
@@ -378,6 +382,10 @@ static void request_send_nowait(struct f
 		fc->num_background++;
 		if (fc->num_background == FUSE_MAX_BACKGROUND)
 			fc->blocked = 1;
+		if (fc->num_background == FUSE_CONGESTION_THRESHOLD) {
+			set_bdi_congested(&fc->bdi, READ);
+			set_bdi_congested(&fc->bdi, WRITE);
+		}
 
 		queue_request(fc, req);
 		spin_unlock(&fc->lock);
Index: linux/fs/fuse/fuse_i.h
===================================================================
--- linux.orig/fs/fuse/fuse_i.h	2007-02-27 14:40:55.000000000 +0100
+++ linux/fs/fuse/fuse_i.h	2007-02-27 14:41:09.000000000 +0100
@@ -20,7 +20,10 @@
 #define FUSE_MAX_PAGES_PER_REQ 32
 
 /** Maximum number of outstanding background requests */
-#define FUSE_MAX_BACKGROUND 10
+#define FUSE_MAX_BACKGROUND 12
+
+/** Congestion starts at 75% of maximum */
+#define FUSE_CONGESTION_THRESHOLD (FUSE_MAX_BACKGROUND * 75 / 100)
 
 /** It could be as large as PATH_MAX, but would that have any uses? */
 #define FUSE_NAME_MAX 1024

--
-
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