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Don't use O_DIRECT when writing WAL files if archiving or streaming is

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enabled. Bypassing the kernel cache is counter-productive in that case,
because the archiver/walsender process will read from the WAL file
soon after it's written, and if it's not cached the read will cause
a physical read, eating I/O bandwidth available on the WAL drive.

Also, walreceiver process does unaligned writes, so disable O_DIRECT
in walreceiver process for that reason too.
This commit is contained in:
Heikki Linnakangas
2010-02-19 10:51:04 +00:00
parent 94f610b163
commit ad458cfe81
4 changed files with 48 additions and 27 deletions
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15
src/include/access/xlogdefs.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/xlogdefs.h,v 1.25 2010/01/15 09:19:06 heikki Exp $
* $PostgreSQL: pgsql/src/include/access/xlogdefs.h,v 1.26 2010/02/19 10:51:04 heikki Exp $
*/
#ifndef XLOG_DEFS_H
#define XLOG_DEFS_H
@@ -106,23 +106,20 @@ typedef uint32 TimeLineID;
* configure determined whether fdatasync() is.
*/
#if defined(O_SYNC)
#define BARE_OPEN_SYNC_FLAG O_SYNC
#define OPEN_SYNC_FLAG O_SYNC
#elif defined(O_FSYNC)
#define BARE_OPEN_SYNC_FLAG O_FSYNC
#endif
#ifdef BARE_OPEN_SYNC_FLAG
#define OPEN_SYNC_FLAG (BARE_OPEN_SYNC_FLAG | PG_O_DIRECT)
#define OPEN_SYNC_FLAG O_FSYNC
#endif
#if defined(O_DSYNC)
#if defined(OPEN_SYNC_FLAG)
/* O_DSYNC is distinct? */
#if O_DSYNC != BARE_OPEN_SYNC_FLAG
#define OPEN_DATASYNC_FLAG (O_DSYNC | PG_O_DIRECT)
#if O_DSYNC != OPEN_SYNC_FLAG
#define OPEN_DATASYNC_FLAG O_DSYNC
#endif
#else /* !defined(OPEN_SYNC_FLAG) */
/* Win32 only has O_DSYNC */
#define OPEN_DATASYNC_FLAG (O_DSYNC | PG_O_DIRECT)
#define OPEN_DATASYNC_FLAG O_DSYNC
#endif
#endif