xv6

commit 843eecfcd0c23f2b9466e5c3289c1819950ccb47
parent 7f1718ca33fb333435b05cd9a0541e6e3b9b7249
Author: Austin Clements <amdragon@mit.edu>
Date:   Mon, 15 Aug 2011 14:11:22 -0400

Only commit log to disk if something was written in to it.

Without this, every write to the console results in log writes.

Diffstat:
M
log.c
 | 
12
+++++++-----

1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/log.c b/log.c
@@ -143,11 +143,13 @@ begin_trans(void)
 void
 commit_trans(void)
 {
-  write_head();        // This causes all blocks till log.head to be commited
-  install_trans();     // Install all the transactions till head
-  log.lh.n = 0; 
-  write_head();        // Reclaim log
-
+  if (log.lh.n > 0) {
+    write_head();        // This causes all blocks till log.head to be commited
+    install_trans();     // Install all the transactions till head
+    log.lh.n = 0; 
+    write_head();        // Reclaim log
+  }
+  
   acquire(&log.lock);
   log.intrans = 0;
   wakeup(&log);