[dtrace-discuss] Re: How to trace process memory usage

[Jim Mauro]

Got it - I didn't realize the window of time between "things are getting 
slow" and
"we're wedged" was so small. I would not start with a DTrace collection
in the back ground.

You could run prstat in collect mode ("prstat -s rss -c 10 > 
/var/tmp/prstat.out" - the
10 is an interval of 10 seconds) in the background. If it's a user land 
process growing,
you'll hopefully capture something before things wedge.

I would also recommend running "kstat -n system_pages 10 > 
/var/tmp/kstat.out"
in the background. You can track the free page list size, and kernel 
pages. Again,
hopefully there will be a trend there we can drill down on before things 
get wedged.

Between those 2, we should be able to determine if it's a user land 
process consuming
memory, or something in the kernel. The next step will be based on what 
that tells
us.

HTH
/jim


Peter Eriksson wrote:
>> prstat(1) is your friend. "prstat -s rss" is a wonderfully simple and effective
>>     
>
> There is only one small problem with that approach - when things are running normally we don't see any strange behaviour. And when things misbehave we typically can't start any new processes (fork: resource temporarily unavailable)...
> Ie, no prstat/vmstat/pmap/top/ps..
>
> That's why we was thinking of using an already running Dtrace to try to "see" what's going on when things are misbehaving...
>
>
> Anyway, I've now increased the available swapspace so it's more than the size of the RAM in the machine and we'll see what happens...
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