Tanel
I must disagree with you. It looks like swap is allocated even for ISM
pages in Solaris. Please feel free to correct me if there is any
misunderstanding from my part.
Here is a small test case:
RS: Intially, 7.4G of swap used
swap -s
total: 7207256k bytes allocated + 233128k reserved = 7440384k used,
40446656k available
RS: ISM in use and SGA is locked as expected.
Address Kbytes RSS Anon Locked Mode
Mapped File
..
0000000380000000 6422544 6422544 - 6422544 rwxsR [
ism shmid=0x300001c ]
RS: No sga_max_size set in spfile either.
strings spfilePROD.ora |grep -i sga
*.sga_target=6272M
RS: Shutting down...
sqlplus "/ as sysdba"
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, Real Application Clusters, OLAP, Data Mining
and Real Application Testing options
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL>
RS: Just 500M of swap used after instance shutdown..
wsqfinc1e> swap -s
total: 451224k bytes allocated + 63928k reserved = 515152k used,
47400568k available
RS: Restarting instance..
ORACLE instance started.
Total System Global Area 6576668672 bytes
Fixed Size 2050464 bytes
Variable Size 2583696992 bytes
Database Buffers 3976200192 bytes
Redo Buffers 14721024 bytes
Database mounted.
Database opened.
RS: Swap is back to 7.32GB
swap -s
total: 7135384k bytes allocated + 191968k reserved = 7327352k used,
40566696k available
RS: Still ISM..
Address Kbytes RSS Anon Locked Mode
Mapped File
...
0000000380000000 6422544 6422544 - 6422544 rwxsR [
ism shmid=0x3000048 ]
Even though, ISM is in use and sga_max_size is not in use, swap is
allocated.
Cheers
Riyaj Shamsudeen
Principal DBA,
Ora!nternals - http://www.orainternals.com
Specialists in Performance, Recovery and EBS11i
Blog: http://orainternals.wordpress.com
On Sat, Aug 1, 2009 at 12:51 AM, Tanel Poder <tanel@xxxxxxxxxx
<mailto:tanel@xxxxxxxxxx>> wrote:
If you use ISM (when SGA_MAX_SIZE = SGA_TARGET or when SGA_MAX_SIZE
is unset in parameter file) then all SGA pages are locked in
physical memory (by OS VM design) - thus no swap space needs to be
reserved as the pages in memory aren't pageable.
If you are using DISM (when SGA_MAX_SIZE > SGA_TARGET) then SGA is
using pageable large pages in Solaris (which are individually locked
in physical memory by Oracle's mlock requests). But as the pages are
essentially pageable, swap space needs to be reserved when SGA is
created.
If you want to avoid your SGA causing the swap space reservation,
unset your SGA_MAX_SIZE parameter.
I have mentioned this on this blog entry (and in the comments
section there's a link to a Solaris kernel internals presentation):
http://blog.tanelpoder.com/2007/08/28/operating-systems-are-lazy-allocating-memory/
--
Tanel Poder
http://blog.tanelpoder.com
On Wed, Jul 29, 2009 at 7:31 AM, Crisler, Jon <Jon.Crisler@xxxxxxx
<mailto:Jon.Crisler@xxxxxxx>> wrote:
On Solaris 10, when I start my databases, I see my swap space
usage increase in a one for one ratio with memory utilization.
System has 64gb of memory. If I start up a 4gb database, I see
4gb of real memory used and 4gb of swap space used up as well
(as shown by top, swap –l, swap –s etc.). This is purely a
Oracle database server, and /etc/system and projects / resource
controls seem to be set up, so I do not understand why swap is
being touched. If I stop all oracle processes, swap drops down
to about 100 Mb used.
I have taken great pains to make sure that NO swap is being
used, yet any little allocation of Oracle gets tossed into
swap. I don’t know where to look after this- I would have
suspected /etc/system or resource control / projects to be at
fault, or /etc/security (ulimits) but everything looks ok.
The system has 64g real, and about 54 gb swap- if I get close
to 54gb memory allocated oracle will return out of memory
errors.. Needless to say the system crawls.
What am I overlooking ? TOP and swap –s / swap –l agree so its
not a TOP anomaly
Example from TOP – I have 20g free, so why so much used in swap ?
load averages: 0.64, 0.57,
0.46
00:26:34
1073 processes:1071 sleeping, 2 on cpu
CPU states: 98.3% idle, 1.2% user, 0.5% kernel, 0.0% iowait,
0.0% swap
Memory: 64G real, 20G free, 40G swap in use, 17G swap free
PID USERNAME LWP PRI NICE SIZE RES STATE TIME CPU
COMMAND
1997 oracle 1 39 0 4376K 2592K cpu/50 0:02 0.04% top
3454 oracle 1 52 0 16G 16G cpu/32 0:00 0.03% oracle
3456 oracle 1 24 0 16G 16G sleep 0:00 0.03%
oracle
18589 oracle 1 59 0 16G 16G sleep 0:13 0.02% oracle
Swap –s
total: 39170184k bytes allocated + 2262264k reserved = 41432448k
used, 18017608k available
--
Tanel Poder
http://blog.tanelpoder.com
