[Cluster-devel] [GFS2 Patch] GFS2: Sort the ordered write list

[Bob Peterson]

Hi,

This patch sorts the ordered write list for GFS2 writes.
This increases the throughput for simultaneous writes.
For example, if you have ten processes, all doing:
dd if=/dev/zero of=/mnt/gfs2/fileX
on different files, the throughput will be much better.

Regards,

Bob Peterson
Red Hat File Systems

Signed-off-by: Bob Peterson <rpeterso at redhat.com> 
--
GFS2: Sort the ordered write list

This patch sorts the ordered write list by block number to speed up
writes.

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 4d31379..b8fe7b7 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -19,6 +19,7 @@
 #include <linux/freezer.h>
 #include <linux/bio.h>
 #include <linux/writeback.h>
+#include <linux/list_sort.h>
 
 #include "gfs2.h"
 #include "incore.h"
@@ -566,6 +567,20 @@ static void log_flush_commit(struct gfs2_sbd *sdp)
 	log_write_header(sdp, 0, 0);
 }
 
+int bd_cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+	struct gfs2_bufdata *bda, *bdb;
+
+	bda = list_entry(a, struct gfs2_bufdata, bd_le.le_list);
+	bdb = list_entry(b, struct gfs2_bufdata, bd_le.le_list);
+
+	if (bda->bd_bh->b_blocknr < bdb->bd_bh->b_blocknr)
+		return -1;
+	if (bda->bd_bh->b_blocknr > bdb->bd_bh->b_blocknr)
+		return 1;
+	return 0;
+}
+
 static void gfs2_ordered_write(struct gfs2_sbd *sdp)
 {
 	struct gfs2_bufdata *bd;
@@ -573,6 +588,7 @@ static void gfs2_ordered_write(struct gfs2_sbd *sdp)
 	LIST_HEAD(written);
 
 	gfs2_log_lock(sdp);
+	list_sort(NULL, &sdp->sd_log_le_ordered, &bd_cmp);
 	while (!list_empty(&sdp->sd_log_le_ordered)) {
 		bd = list_entry(sdp->sd_log_le_ordered.next, struct gfs2_bufdata, bd_le.le_list);
 		list_move(&bd->bd_le.le_list, &written);