I have modified your patch (attached) and will apply soon, unless there
are more community comments. Thanks.
---------------------------------------------------------------------------
ITAGAKI Takahiro wrote:
> Bruce Momjian <[email protected]> wrote:
>
> > > > > Here is a small patch to prevent undesired WAL file caching by kernel.
> > > > > posix_fadvise(POSIX_FADV_DONTNEED) attempts to free cached pages and
> > > > > the kernel will discard them in preference to other data caches.
> > > >
> > > > On plenty of platforms, this won't even compile ...
> >
> > Yes, but we probably have to have a configure test to see if
> > posix_fadvise exists too. I will keep this for 8.2.
>
> I think we can use _POSIX_ADVISORY_INFO to test if posix_fadvise exists.
> Also, I added the check on whether WAL archiving is enabled, because
> archivers might use the caches to read the WAL segment.
>
>
> By the way, should we put posix_fadvise on the separated place with renaming
> pg_fadvise? If we use posix_fadvise in other purposes, for example,
> read-ahead control, the separation would be good to keep codes clean.
>
> ---
> ITAGAKI Takahiro
> NTT Cyber Space Laboratories
>
[ Attachment, skipping... ]
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match
--
Bruce Momjian http://candle.pha.pa.us
EnterpriseDB http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
Index: src/backend/access/transam/xlog.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v
retrieving revision 1.237
diff -c -c -r1.237 xlog.c
*** src/backend/access/transam/xlog.c 20 Apr 2006 04:07:38 -0000 1.237
--- src/backend/access/transam/xlog.c 14 Jun 2006 17:38:10 -0000
***************
*** 478,483 ****
--- 478,484 ----
bool use_lock);
static int XLogFileOpen(uint32 log, uint32 seg);
static int XLogFileRead(uint32 log, uint32 seg, int emode);
+ static void XLogFileClose(void);
static bool RestoreArchivedFile(char *path, const char *xlogfname,
const char *recovername, off_t
expectedSize);
static int PreallocXlogFiles(XLogRecPtr endptr);
***************
*** 1384,1397 ****
*/
Assert(npages == 0);
if (openLogFile >= 0)
! {
! if (close(openLogFile))
! ereport(PANIC,
!
(errcode_for_file_access(),
! errmsg("could not close log
file %u, segment %u: %m",
! openLogId,
openLogSeg)));
! openLogFile = -1;
! }
XLByteToPrevSeg(LogwrtResult.Write, openLogId,
openLogSeg);
/* create/use new log file */
--- 1385,1391 ----
*/
Assert(npages == 0);
if (openLogFile >= 0)
! XLogFileClose();
XLByteToPrevSeg(LogwrtResult.Write, openLogId,
openLogSeg);
/* create/use new log file */
***************
*** 1567,1580 ****
{
if (openLogFile >= 0 &&
!XLByteInPrevSeg(LogwrtResult.Write, openLogId,
openLogSeg))
! {
! if (close(openLogFile))
! ereport(PANIC,
!
(errcode_for_file_access(),
! errmsg("could not close log
file %u, segment %u: %m",
! openLogId,
openLogSeg)));
! openLogFile = -1;
! }
if (openLogFile < 0)
{
XLByteToPrevSeg(LogwrtResult.Write, openLogId,
openLogSeg);
--- 1561,1567 ----
{
if (openLogFile >= 0 &&
!XLByteInPrevSeg(LogwrtResult.Write, openLogId,
openLogSeg))
! XLogFileClose();
if (openLogFile < 0)
{
XLByteToPrevSeg(LogwrtResult.Write, openLogId,
openLogSeg);
***************
*** 2153,2158 ****
--- 2140,2173 ----
}
/*
+ * Close the current logfile segment for writing.
+ */
+ static void
+ XLogFileClose(void)
+ {
+ Assert(openLogFile >= 0);
+
+ #ifdef _POSIX_ADVISORY_INFO
+ /*
+ * WAL caches will not be accessed in the future, so we advise OS to
+ * free them. But we will not do so if WAL archiving is active,
+ * because archivers might use the caches to read the WAL segment.
+ * While O_DIRECT works for O_SYNC, posix_fadvise() works for fsync()
+ * and O_SYNC, and some platforms only have posix_fadvise().
+ */
+ if (!XLogArchivingActive())
+ posix_fadvise(openLogFile, 0, 0, POSIX_FADV_DONTNEED);
+ #endif
+
+ if (close(openLogFile))
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not close log file %u, segment %u: %m",
+ openLogId, openLogSeg)));
+ openLogFile = -1;
+ }
+
+ /*
* Attempt to retrieve the specified file from off-line archival storage.
* If successful, fill "path" with its complete path (note that this will be
* a temp file name that doesn't follow the normal naming convention), and
***************
*** 5609,5622 ****
errmsg("could not fsync log
file %u, segment %u: %m",
openLogId,
openLogSeg)));
if (open_sync_bit != new_sync_bit)
! {
! if (close(openLogFile))
! ereport(PANIC,
!
(errcode_for_file_access(),
! errmsg("could not close log
file %u, segment %u: %m",
! openLogId,
openLogSeg)));
! openLogFile = -1;
! }
}
sync_method = new_sync_method;
open_sync_bit = new_sync_bit;
--- 5624,5630 ----
errmsg("could not fsync log
file %u, segment %u: %m",
openLogId,
openLogSeg)));
if (open_sync_bit != new_sync_bit)
! XLogFileClose();
}
sync_method = new_sync_method;
open_sync_bit = new_sync_bit;
---------------------------(end of broadcast)---------------------------
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