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

[Martin T]

I did some additional research and while the swapfile in /etc/rc.conf
is disabled:

root at M5% grep -i swap /etc/rc.conf
swapfile="NO"           # Set to name of swapfile if aux swapfile desired.
root at M5%

..then this does not affect swap partition entries in /etc/fstab file.
swapon utility is present and top would display "Swap: " instead of
"Swap: 512M Total, 512M Free" if there is no swap partition/file. In
addition, I tested with another routing-engine(RE-600 with 256MiB RAM)
and once I consumed more than 95% of memory, it indeed started to use
swap partition.


regards,
Martin


2013/4/3, Martin T <m4rtntns at gmail.com>:
> 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
>