Hi,
This will clear your dobut hopefully..
swapinfo description and example...
Use 'swapinfo -tm' to get a complete/total picutre of swap usage (see below for example and details.) Pay particular attention to the total line as it indicates how much swap space has been actually reseved for swap. When this percentage gets near 100%, processes will not start up (unable to fork process) and new shared memory segments can not be created.
swapinfo -tm example and explanation:
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 288 83 205 29% 0 - 1 /dev/vg00/lvol2
reserve - 141 -141
memory 102 41 61 40%
total 390 265 125 68% - 0 -
dev line(s):
are the actual physical swap device(s)
show if swapping has actually occurred. In other words, the PCT USED column in the dev lines represents the value last attained during a previous period of swapping. This is analogous to the high-water mark that a flood leaves.
to check to see if swapping is currently occuring, use 'vmstat -v 5 5' to see if the 'po' (page outs) is sustained above 0.
reserve line(s)
indicate how much of the swap device(s) has(have) been set aside for memory should it need to be swapped.
memory line:
indicative of how much of pseudo-swap has been reserved
when present, indicates pseudo-swap is enabled (i.e. swapmem_on kernel paraemter is set to 1, which is the default.) The size of pseudoswap is calculated to be 75% of the size of RAM (a.k.a. memory.) In other words, it does not refer to acual physical memory use!!!! Pseudo-swap was designed specifically for large memory systems for which acutal swapping is never (or rarely) expected to occur, so thereâ s less need to use actual physical disk space for swap. For more information, see swapmem_on(5) , which reads:
In previous versions of HP-UX, system configuration required sufficient physical swap space for the maximum possible
number of processes on the system. This is because HP-UX reserves swap space for a process when it is created, to
ensure that a running process never needs to be killed due to insufficient swap.
This was difficult, however, for systems needing gigabytes of swap space with gigabytes of physical memory, and those
with workloads where the entire load would always be in core. This tunable was created to allow system swap space to
be less than core memory. To accomplish this, a portion of physical memory is set aside as 'pseudo-swap' space.
While actual swap space is still available, processes still reserve all the swap they will need at fork or execute time from
the physical device or file system swap. Once this swap is completely used, new processes do not reserve swap, and
each page which would have been swapped to the physical device or file system is instead locked in memory and
counted as part of the pseudo-swap space.
total line:
the PCT USED value shown in the total line indicates how much swap space has been actually reseved for swap. When this percentage gets near 100%, processes will not start up (unable to fork process) and new shared memory segments can not be created.
Best wishes,
Ganesh.
