Arrange to align shared disk buffers on at least 32-byte boundaries,

not just MAXALIGN boundaries.  This makes a noticeable difference in
the speed of transfers to and from kernel space, at least on recent
Pentiums, and might help other CPUs too.  We should look at making
this happen for local buffers and buffile.c too.  Patch from Manfred Spraul.

1 files changed, 9 insertions, 1 deletions

diff --git a/src/include/pg_config_manual.h b/src/include/pg_config_manual.h
index 451ef351e65..98d357760dc 100644
--- a/src/include/pg_config_manual.h
+++ b/src/include/pg_config_manual.h
@@ -6,7 +6,7 @@
  * for developers.	If you edit any of these, be sure to do a *full*
  * rebuild (and an initdb if noted).
  *
- * $Id: pg_config_manual.h,v 1.5 2003/08/04 00:43:29 momjian Exp $
+ * $Id: pg_config_manual.h,v 1.6 2003/09/21 17:57:21 tgl Exp $
  *------------------------------------------------------------------------
  */
 
@@ -127,6 +127,14 @@
 #define BITS_PER_BYTE		8
 
 /*
+ * Preferred alignment for disk I/O buffers.  On some CPUs, copies between
+ * user space and kernel space are significantly faster if the user buffer
+ * is aligned on a larger-than-MAXALIGN boundary.  Ideally this should be
+ * a platform-dependent value, but for now we just hard-wire it.
+ */
+#define ALIGNOF_BUFFER	32
+
+/*
  * Disable UNIX sockets for those operating system.
  */
 #if defined(__QNX__) || defined(__BEOS__) || defined(WIN32)