Following up (the offline exchange wasn't intended), cutting the
principal buffer down to 4k gave a startup time around 10 seconds, and
cutting the agg buffer down to 32k in addition cut it down to seven.
That's close enough to 4*(T5220 behavior) to satisfy me (though it would
be very nice if it were more scalable...).
Regards,
Ryan
On 2/20/2010 11:24 AM, Jon Haslam wrote:
Just for the record, I had an offline exchange with Ryan on this.
The startup time when using dtrace(1M) on systems with many
CPU's such as the T5440 can be large owing to the default
principal and aggregation buffer sizes (4MB). To reduce the
startup latency, tune these down (if possible) by setting the
`bufsize` and `aggsize` tunables accordingly. Obviously, if you
set them too low then you'll see drops reported.
Really, dtrace(1M) needs to be smarter about how much memory
it's asking for in these large configs.
Jon.
We just got a shiny new T5440, and one of the first things I noticed
(besides the insane number of hardware contexts), is that dtrace
takes 30 seconds to a minute to fire up scripts with 5-6 probes,
where our T5220 usually takes under a second. Shutdown is similar,
though slightly faster.
This is mostly annoying because it takes so long to attach that it's
hard to tell when I've collected enough data to be useful. I've
started using BEGIN and END probes to prun stopped instances of
'echo' so I can see when probing actually starts and ends...
Any idea why this should be the case? I'm running S10 (142900-03).
Thanks,
Ryan
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