low swap but high memory

Well, those stats are a bit extreme, but not impossible.

Solaris will push out to swap any memory that has been allocated but doesnt appear to be being used.

So its pushed out 57G of useless crap.

It does this to free up memory for more useful tasks.

It may look like you've got 13 Gig of free memory just sitting around doing nothing. But the "free" memory is actually used as a disk cache. So you have 13 Gig of memory being used to cache hopefully more useful data than the 57 Gig of crap it pushed out to swap..

Anyway, low swap isnt actually a critical problem. Its not ideal, certainly. Because it indicates that the could be even more crap taking up memory that it would push out to swap if it could.

But low memory would be much more of a problem. Because that indicates that that the system has more useful data than memory and so has been forced to push out to swap stuff it would prefer to keep in memory...

So you could add some more swap if its convenient. But its not critical. A more useful question is why is so much virtual memory being allocated and why isnt it being used. Perhaps you can tune your application to grab less memory.

robert.cohena at 2007-7-12 23:10:06 >

I nearly hit post before actually testing out the command on my own systems, but I nearly stated my standard statement (stolen from another SA) - that top has been relatively broken since at least 2.5 days -

I think that statement really drives to the "freemem" parameter and other kernel memory statistics areas that in older versions of Solaris really didn't contain as much "relevant" info as it does in more recent versions. [ edit - on version 2.8 and above, freemem appears to be fixed and top is reporting things correctly now ]

take for example this following 2.6 example -

$ df -k /tmp

Filesystemkbytesusedavail capacity Mounted on

swap655544853760 65016881%/tmp

$ swap -l

swapfile dev swaplo blocksfree

/dev/vx/dsk/swapvol 156,516 3071984 2608576

$ prtconf |egrep "^Memory"

Memory size: 7168 Megabytes

$ egrep swap /etc/vfstab

/dev/vx/dsk/swapvol--swap-no-

swap-/tmptmpfs-yes-

these lines show that I'm not limiting at mount time my tmpfs filesystem, that I have ~7GB of memory on the machine, another 1.5GB of file mounted swap and have roughly 6.5GB total available remaining "memory" on the machine whether its physical mounted swap or RAM.

the top output shows (cutting for relevance)

load averages: 0.03, 0.04, 0.05;up 140+03:07:05 13:24:59

86 processes: 85 sleeping, 1 on cpu

CPU states: 98.5% idle, 0.0% user, 1.5% kernel, 0.0% iowait, 0.0% swap

Memory: 7168M phys mem, 120M free mem, 1500M swap, 1274M free swap

###

and the 120M free mem seems way out of place -

however, if you look at the vmstat 5 5 |tail -1 output (keeping my header lines)

$ vmstat 5 5 |tail -1

procsmemorypagedisk faultscpu

r b wswap free re mf pi po fr de sr s2 s7 s7 s8insycs us sy id

0 0 30 6503856 123160 0 0 0 0 0 0 0 0 0 0 1 828 127 216 0 0 100

there you see my "freemem" value

ftp://ftp.sunfreeware.com/pub/freeware/sparc/9/top-3.6.1-sol9-sparc-local.gz

Try downloading top for Solaris 9 if this is for a Solaris 9 machine. If your OS isn't 2.9, then please let us know which version we're actually talking about

thanks! - jeff

Message was edited by: jeff

jeffrey.s

jeffrey.sa at 2007-7-12 23:10:06 >

even though - in my 2.6 example vmstat and top match their "freemem" - doesn't mean it's the reporting the same thing as on a 2.8/2.9 vmstat/top output of freemem. We're saying the same thing - the VM system information has greatly changed what is being reported 2.8 and later.

The example from the original post - to me - looks like it's pre 2.8 based on similar results on an older platform machine - even though they didn't explictly state version in their post - jeff

jeffrey.sa at 2007-7-12 23:10:06 >