kmeminfo - Dynamic memory

[scifusers]

Hi,

Our system shows high system memory usage. From the kmeminfo, dynamic memory usage is high. Is there any way(kernel parms??) to reduce it? We want to migrate this system to new hardware where we have only 6 gb.

Physical memory usage summary (in page/byte/percent):

Physmem = 5242880 20.0g 100% Physical memory
Freemem = 3392967 12.9g 65% Free physical memory
Used = 1849913 7.1g 35% Used physical memory
System = 1147089 4.4g 22% By kernel:
text = 2796 10.9m 0% text
data = 753 2.9m 0% data
bss = 7507 29.3m 0% bss
Static = 279896 1.1g 5% for text/static data
Dynamic = 594632 2.3g 11% for dynamic data
Bufcache = 262144 1.0g 5% for buffer cache
Eqmem = 95 380.0k 0% for equiv. mapped memory
SCmem = 10322 40.3m 0% for critical memory
User = 707321 2.7g 13% By user processes:
Uarea = 11196 43.7m 0% for thread uareas
Disowned = 8 32.0k 0% Disowned pages

----------------------------------------------------------------------
Kernel dynamic memory usage (in page/byte/percent):

Physmem = 5242880 20.0g 100% Physical memory
Freemem = 3392967 12.9g 65% Free memory
Used = 1849913 7.1g 35% Used memory
Dynamic = 594632 2.3g 11% Kernel dynamic memory
Arenas = 539619 2.1g 10% Kernel arenas
M_TEMP = 454164 1.7g 9%
M_SPINLOCK = 41078 160.5m 1%
M_SWAP = 8432 32.9m 0%
KMEM_ALLOC = 6263 24.5m 0%
M_IOSYS = 5868 22.9m 0%
VFD_BT_NODE = 3711 14.5m 0%
VM MISC ARENA = 2065 8.1m 0%
ALLOCB_MBLK_LM = 1985 7.8m 0%
M_REG = 1658 6.5m 0%
M_PREG = 1574 6.1m 0%
M_KTHREAD = 1451 5.7m 0%
ALLOCB_MBLK_DA = 1093 4.3m 0%
M_NFS_GEN = 1019 4.0m 0%
M_LVM = 821 3.2m 0%
LVM_PBUF = 785 3.1m 0%
Other = 7652 29.9m 0% Other arenas...
Kalloc = 54917 214.5m 1% kalloc()
SuperPagePool = 5332 20.8m 0% Kernel superpage cache
BufcacheBufs = 27184 106.2m 1% Buffer cache bufs
BufcacheHash = 20480 80.0m 0% Buffer cache hash heads
Other = 1921 7.5m 0% Other...
Eqalloc = 96 384.0k 0% eqalloc()

[Steven E. Protter]

Shalom,

Reduce memory use by changing kernel parameters.

Well, memory is used by applications. Oracle has for example SGA settings that permit you to tell it to do less or more memory use. I'd look at the application first and then the buffer cache.

dbc_max_pct
dbc_min_pct

Should be close to each other and lower to reduce memory use.

SEP

[Bill Hassell]

Well, taking a system that is performing well with 20Gb and reducing the RAM to 6Gb in the new server can be done without changing anything except making sure you have enough swap space -- and a *LOT* of time to wait for the system.

There is nothing useful to tune in the kernel for this 70% drop in RAM except perhaps the dynamic buffer cache max% (dbc_max_pct) which is always misconfigured at 50%. For 6Gb, you'll need to set the dbc_max_pct value to about 15 percent. Now if you are running a modern database such as Sybase or Oracle, your database admin will have to reduce the shared memory areas by about 70% too. Oh, performance will experience a drastic performance hit.

RAM is what makes modern applications run at a reasonable speed. Remove the RAM and while the programs will still run, response time will make the programs almost unuseable.