swap file not present

Hello all,

We are running a 2 gig Solaris10 system. The only application that's running on the system is ours which allocates 850MB through malloc at one shot.

For some reason this malloc keeps failing saying "Resource Temporarily Unavilable"

After some investigation, found that it goes away when a swap file is added. But that is not the goal. We would want the app to run without any disk i/o or any page reloads. Everything should be off the physical memory.

Any inputs?

The config is as below
# swap -s
total: 52040k bytes allocated + 4648k reserved = 56688k used, 1542344k available

# swap -l
No swap devices configured

# vmstat 2
kthr memory page disk faults cpu
r b w swap free re mf pi po fr de sr s0 -- -- -- in sy cs us sy id
0 0 0 1498888 1706336 2 17 6 0 0 0 4 1 0 0 0 2361 234 271 0 0 100
0 0 0 1542152 1561576 0 4 0 0 0 0 0 0 0 0 0 2090 222 68 0 0 100
0 0 0 1542080 1561504 0 0 0 0 0 0 0 0 0 0 0 2078 106 55 0 0 100

# prtconf | grep Memory
Memory size: 2040 Megabytes

Assuming the OS needs 700MB to stand up and 300MB for other misc purposes, there is still 1 gig left, why does it need a swap file? Where has all my memory gone

# prstat -a
PID USERNAME SIZE RSS STATE PRI NICE TIME CPU PROCESS/NLWP
542 root 4816K 4808K cpu1 59 0 0:00:00 0.0% prstat/1
445 root 2744K 2224K sleep 59 0 0:00:18 0.0% vmstat/1
194 root 2112K 1480K sleep 59 0 0:00:00 0.0% sac/1
168 root 2704K 1328K sleep 59 0 0:00:00 0.0% cron/1
325 root 6904K 5384K sleep 59 0 0:00:00 0.0% sshd/1
203 root 3728K 2112K sleep 59 0 0:00:00 0.0% syslogd/13
183 daemon 2712K 1888K sleep 59 0 0:00:00 0.0% rpcbind/1
92 root 4248K 3680K sleep 59 0 0:00:00 0.0% nscd/24
193 root 1360K 1160K sleep 59 0 0:00:00 0.0% utmpd/1
529 root 1336K 1232K sleep 59 0 0:00:00 0.0% sh/1
186 root 9608K 8000K sleep 59 0 0:00:02 0.0% fmd/16
70 root 2560K 1864K sleep 59 0 0:00:00 0.0% syseventd/12
9 root 7072K 5192K sleep 59 0 0:00:08 0.0% svc.configd/12
7 root 15M 12M sleep 59 0 0:00:07 0.0% svc.startd/12
96 daemon 4360K 3000K sleep 59 0 0:00:00 0.0% kcfd/5
NPROC USERNAME SIZE RSS MEMORY TIME CPU
31 root 144M 101M 5.1% 0:00:38 0.0%
2 daemon 7072K 4888K 0.2% 0:00:00 0.0%

Any help would be great.

Thanks

2 GB is not very much memory. By your estimate the OS is using 700MB + 300MB = 1 GB. You have 1 GB left for your app. You want to malloc 850 MB. Now you have 150 MB left for the rest of your app. And you wonder where your memory went?

You prefer that your app not swap. Well, welcome to the club. But suppose you somehow run out of memory... what should happen then? You have two choices:

1) allocate some swap so your app will continue run, albeit slower than you would like
2) allocate no swap so your app will reliably crash and burn should you run out of memory

perderabo,
Well, come to think of it, there is a way to ensure everything is resident and nothing is paged by using mlockall() in your app. But, seems like this is not working without any swap file!!

If you read Perderabo's reply again you will understand why.

If you have no swap, where will the other objects in memory page to?

What other objects? as i mentioned before the only app on the sytem is ours. Presuming an extremely high requirement of main memory by the OS, to be 700MB and adding another 300MB for leeway. What else does the system need?

I really doubt if the OS needs 1 Gb to sustain itself. What's your though? How can I peek into the memory to see what is eating how much? Cause as pasted above, I dont see any daunting processes gobbling memory, except ours when its started of course

Ok, let's for a minute assume you are correct and there is no need for swap, and go about this from the other side and just to rule it out, your application doesn't do something silly like malloc 850Mb then fork ?

Reborg

The app eats 1G max, not more than that.
And no forking or execing in there.
With things running fine, I observed the RSS for my app and the max it goes is 1gig.

can you post a truss output from running the app with no swap device?