[j-nsp] understanding M5 RE-333-256 memory usage

[Martin T]

Hi,

I have a Juniper M5(8.5R4.3) with RE-333-256 routing-engine in remote
location. I guess it has either 1x 256MiB PC66/PC100/PC133 SDRAM or 2x
128MiB PC66/PC100/PC133 SDRAM memory-modules. Under "show chassis
routing-engine" output memory utilization is 90%:

root at M5> show chassis routing-engine | match memory
    Memory utilization          90 percent

root at M5>


During that time "show system processes summary"(basically "top -d 1
stats" front-end) displays following information:

root at M5> show system processes summary
last pid: 38083;  load averages:  0.19,  0.05,  0.02  up 1163+04:59:05
   16:11:54
104 processes: 3 running, 85 sleeping, 16 waiting

Mem: 70M Active, 105M Inact, 39M Wired, 11M Cache, 34M Buf, 13M Free
Swap: 512M Total, 512M Free


  PID USERNAME     THR PRI NICE   SIZE    RES STATE    TIME   WCPU COMMAND
   11 root           1 171   52     0K    12K RUN       ??? 97.75% idle


root at M5>


Why is swap space usage 0% while memory usage is high? Is it because
there is actually no swap in use? On the other hand, according to
/etc/fstab file, the swap space is on HDD:

/dev/ad1s1b    none        swap    sw        0    0



In addition, according to "show system boot-messages", the "available
memory" is 237MiB:

real memory  = 268369920 (255 MB)
avail memory = 248852480 (237 MB)

Why is this so? Where is the 18.6MiB reserved?



regards,
Martin