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From: Jeff Roberson <jeff@FreeBSD.org>
Date: Tue, 13 Mar 2018 03:54:42 +0000 (UTC)
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Subject: svn commit: r330828 - user/jeff/numa/sys/kern
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Author: jeff
Date: Tue Mar 13 03:54:41 2018
New Revision: 330828
URL: https://svnweb.freebsd.org/changeset/base/330828

Log:
  Most of the time bufspace_adjust() shouldn't be adjusting anything.  In
  this case don't waste time on an expensive atomic.

Modified:
  user/jeff/numa/sys/kern/vfs_bio.c

Modified: user/jeff/numa/sys/kern/vfs_bio.c
==============================================================================
--- user/jeff/numa/sys/kern/vfs_bio.c	Tue Mar 13 03:53:33 2018	(r330827)
+++ user/jeff/numa/sys/kern/vfs_bio.c	Tue Mar 13 03:54:41 2018	(r330828)
@@ -613,7 +613,7 @@ bufspace_adjust(struct buf *bp, int bufsize)
 	diff = bufsize - bp->b_bufsize;
 	if (diff < 0) {
 		atomic_subtract_long(&bd->bd_bufspace, -diff);
-	} else {
+	} else if (diff > 0) {
 		space = atomic_fetchadd_long(&bd->bd_bufspace, diff);
 		/* Wake up the daemon on the transition. */
 		if (space < bd->bd_bufspacethresh &&