How to analyse Swap/Memory usage Oracle Solaris?


Memory bottlenecks are evidenced by two different things happening on the system.

  • Paging
    • Page in;something is moved into Active RAM whether that is from Inactive RAM, the swapfile(s), or another file on the hard drive.
      • Page out;anything is moved out from Active RAM to Inactive RAM, as well as writing to a Swapfile. Also in some cases, high  page  out means your system has run out of memory and had to use some of the Hard Disk instead of RAM.
  • Swapping

Paging refers to memory pages being reclaimed by the system page daemon, when system faces with lack of free memory.Swapping is more extreme and it means that processed being swapped out. Determine if system is only paging or swapping you should check two columns in “vmstat” output. The first result you need to check is “scan rate (sc)”.If this result is different from “0” then it means page daemon scans for free memory pages to put in them on the free list to be reused.

Page scan runs: default value is 1/64th of total physical memory or cache free.

Don’t worry about high scan rate if you are using the file system heavily. If priority_paging is enable high scan rate can be normal in many circumstances. If priority_paging is enabled then page scanners daemon steals pages more effectively. So the file system I/O does not cause unnecessary paging of process.

Check “w” column to see if system is swapping. It shows entire processes which are swapped out. If “w” column is different from 0, system is either low on memory right now, or have been in the past.

Use this command to see which processes are running .Don’t forget that check for RSS column if it’s 0 (sched, pageout and fsflush processes should always have a RSS of 0). If not then it means that system is swapping out.


Scan Rate And “w” Column:

#vmstat 1 2



kthr memory page disk faults cpu



r b w swap free re mf pi po fr de sr lf lf s2 s3 in sy cs us sy id



0 0 5 2304856 1352240 128 318 0 0 0 0 5 0 0 -0 5 661 28851 667 78 4 18



0 0 22 3802064 3028192 27 33 0 0 0 0 0 0 0 0 0 623 35757 466 98 2 0

RSS  check: RSS  column must be “0”  for this check.If not system is low on memory right now.

 

#/usr/bin/ps -e -o pid,rss,args|egrep 'sched|pageout|fsflush'|grep -v grep



PID     RSS      COMMAND

0        0        sched

2        0        pageout

3        0        fsflush

Page Out, Page in:

 

# vmstat 1 5|awk '{print $8 " " $9}'

pi po

325 1942

0 6581

0 6376

0 5851

0 6576

Check Free Memory: 

 

# sar -r 1 1000



SunOS opscgmrtep00 5.10 Generic_150400-18 sun4v 10/16/2015



16:08:58 freemem freeswap

16:08:59 116382376 2015530288

How to calculate  sar free memory  usage?

 
Parameter Size Total Free  Size
Free Mem GB Free  Memory*8  /1024/1024/1024
Free Swap GB Free  Swap * 512 /1024 /1024/1024

Pagesize for Oracle  Solaris  is  8K.
How to check  page size  on Oracle Solaris ?

# pagesize

8192

How to check free  memory  on Oracle  Solaris?

#echo  ::memstat|mdb  -k



Page Summary                Pages                MB  %Tot



------------     ----------------  ----------------  ----



Kernel                     653403              5104    8%



ZFS File Data             1062828              8303   13%



Anon                      3278738             25615   40%



Exec and libs               19061               148    0%



Page cache                 153244              1197    2%



Free (cachelist)            18087               141    0%



Free (freelist)           3050836             23834   37%







Total                     8236197             64345



Physical                  8190736             63990

How  to check process  memory  usage  on Oracle Solaris?

This  command will sort  processes  by memory usage(RSS ).If you need change sort  option for  Virtual Size.

# ps  -ely|grep  -v  PID|sort  -nrk8|more

 

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