[SunHELP] Physical memory used on a Sun 3800

[DAUBIGNE Sebastien - BOR ( SDaubigne@bordeaux-bersol.sema.slb.com )]

Starting from Solaris 8, the file cache and the anonymous memory use a
separate free list. This new architecture avoids freeing anonymous memory to
the swap device when you do heavy I/O and the file cache is still large.
Another consequence is that high vmstat "sr" values indicates a memory
shortage (like other Unix), which was not necessary the case with pre-8
Solaris versions (because there was high "sr" value when you did heavy I/O).
There is a good URL which explains the differences between the former and
the new memory algorithm  :

http://soldc.sun.com/articles/sol8memory.html
<http://soldc.sun.com/articles/sol8memory.html>

The best tool I know for monitoring memory utilisation is the SUN RMCmem
package, which is available for Solaris 2.6,2.7,8,9.
To get this package, send a mail to memtool-request at chessie.eng.sun.com
<mailto:memtool-request at chessie.eng.sun.com>
I still don"t understand why Sun does not bundle this product with Solaris,
or at least does not put in on its Web site as free download.

Additionnal informations about RMCmem can be obtained in the following URL :

http://www.sun.com/sun-on-net/itworld/UIR980301perf.html
<http://www.sun.com/sun-on-net/itworld/UIR980301perf.html>
http://www.sun.com/sun-on-net/performance/vmsizing.pdf
<http://www.sun.com/sun-on-net/performance/vmsizing.pdf>

---
Sebastien DAUBIGNE
sdaubigne at bordeaux-bersol.sema.slb.com
<mailto:sdaubigne at bordeaux-bersol.sema.slb.com>  - (+33)5.57.26.56.36
SchlumbergerSema - SGS/DWH/Pessac

	-----Message d'origine-----
	De:	Simoncini, Matthew [SMTP:Matthew.Simoncini at bsci.com]
	Date:	mardi 14 janvier 2003 20:22
	@:	'sunhelp at sunhelp.org'
	Objet:	[SunHELP] Physical memory used on a Sun 3800

	Hello gurus,

	We've just taken over the management of a couple SunFire 3800
servers
	running Solaris 8 and I was looking for some options on capturing
memory
	utilization. As I understand systems running pre-Solaris8 there is
something
	called "file buffer cache" or "file system buffer" that utilizes
"unused"
	physical memory to cache file system information. This "file buffer
cache"
	causes utilities like vmstat to show very low free memory when in
fact
	that's not the case. Again my understanding is that Solaris will
free memory
	for other applications from the "file system cache" when
applications need
	it.

	Now is it true that the free column in vmstat under Solaris 8/9
gives you a
	more meaningful number in terms of actual memory free?

	If someone could set me in the right direction in terms of the best
method
	for determining memory utilization on Solaris 8/9 systems, it would
be
	greatly appreciated.

	Matthew
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