Physical Memory

[Mohammad Sanaullah]

Dear All !!!

Once again i am here related to memory....
can any one tell me what exactly i count to show the user about physical memory utilization i.e. as output of vmstat -P says out of 3072 MB RAM Physical Memory used is 3069.97 MB is it??? and also shows that it uses only 20-30 % of SWAP.

Still free Pages accounts for 3-5% of memory i.e used memory is only 95-97% then why system shows 99.97% memory utilized..

How can i answer to customer that how much Physical Memory is utilized by system. is it should be based on vmstats physical memory used or free pages accounted for Memory Available???
Please any one tell me any book which can clear me understanding the Memory utilization by tru64 OS.

Waiting for Response!!!

[Ivan Ferreira]

You can use vmstat or collect -sm (which displays memory information in MB).

From section 12-17 of System configuration and tuning manual:

Output of vmstat:

The sum of the free, active, and wired pages should be close to the amount of physical memory in your system. Although the value for
free should be small, if the value is onsistently small (less than 128
pages) and accompanied by excessive paging and swapping, you may not have enough physical memory for your workload.

Now, the swap usage depends of the swap_eager value. If set to 1, process will reserve space, you can check if swap is reserved from the output of swapon -s.

[Venkatesh BL]

Can you post the vmstat output, if possible?

[Mohammad Sanaullah]

Total Physical Memory = 3072.00 M
= 393216 pages

Physical Memory Clusters:

start_pfn end_pfn type size_pages / size_bytes
0 256 pal 256 / 2.00M
256 130729 os 130473 / 1019.32M
130729 131072 pal 343 / 2.68M
131072 393212 os 262140 / 2047.97M
393212 393216 pal 4 / 32.00k

Physical Memory Use:

start_pfn end_pfn type size_pages / size_bytes
256 521 scavenge 265 / 2.07M
521 1509 text 988 / 7.72M
1509 1723 data 214 / 1.67M
1723 2214 bss 491 / 3.84M
2214 2470 kdebug 256 / 2.00M
2470 2477 cfgmgmt 7 / 56.00k
2477 2479 locks 2 / 16.00k
2479 2495 pmap 16 / 128.00k
2495 3918 unixtable 1423 / 11.12M
3918 3966 logs 48 / 384.00k
3966 7129 vmtables 3163 / 24.71M
7129 131072 managed 123943 / 968.30M
131072 137076 vmtables 6004 / 46.91M
137076 393212 managed 256136 / 2001.06M
============================
Total Physical Memory Use: 392956 / 3069.97M

Managed Pages Break Down:

free pages = 29424
active pages = 125161
inactive pages = 100434
wired pages = 48830
ubc pages = 76152
==================
Total = 380001

WIRED Pages Break Down:

vm wired pages = 4852
ubc wired pages = 0
meta data pages = 11721
malloc pages = 26540
contig pages = 1410
user ptepages = 3649
kernel ptepages = 394
free ptepages = 4
==================
Total = 48570

-----------------------------------------------------------------
vmstat 5 5

Virtual Memory Statistics: (pagesize = 8192)
procs memory pages intr cpu
r w u act free wire fault cow zero react pin pout in sy cs us sy id
5 486 134 293K 37K 48K 2G 217M 1G 419K 214M 3252 956 6K 2K 18 7 75
4 486 134 292K 38K 48K 999 167 479 0 256 0 882 5K 3K 21 5 74
5 486 134 293K 38K 48K 808 215 223 0 197 0 1K 4K 4K 15 5 80
4 490 133 293K 37K 48K 1795 131 780 0 274 0 491 4K 1K 12 5 83
5 488 132 293K 38K 48K 357 138 309 0 221 0 334 6K 1K 25 2 73
------------------------------------------------------------------------------------
swapon -s

Swap partition /dev/disk/dsk5b (default swap):
Allocated space: 31104 pages (243MB)
In-use space: 8483 pages ( 27%)
Free space: 22621 pages ( 72%)

Swap partition /dev/disk/dsk24c:
Allocated space: 1110845 pages (8.48GB)
In-use space: 8595 pages ( 0%)
Free space: 1102250 pages ( 99%)


Total swap allocation:
Allocated space: 1141949 pages (8.71GB)
Reserved space: 309388 pages ( 27%)
In-use space: 17078 pages ( 1%)
Available space: 832561 pages ( 72%)

[Venkatesh BL]

1) The "Total Physical Memory Use" field represents the total memory present for use by the OS -- NOT the total memory already used up by the processes!

Its roughly the sum of:
256 130729 os 130473 / 1019.32M <<<
131072 393212 os 262140 / 2047.97M <<<

2) For process specific memory usage, you could use 'ps' or 'collect'

3) Swap space usage looks normal. 'Reserved space' value could be because of the 'eager' mode.

4) In vmstat output, the 'pout' field is important. Here it is '0', which means that no pageouts are happening on the system - which is good.