Thursday September 09, 2004
Thursday September 09, 2004
dtrace - ticks!
I have a lot of fun when I see Bryan making his dtrace demos. They're all cool, he says type this in: dtrace -i 'syscall:::entry { @[execname] = count() }', press enter, wait a few seconds and then hit control-c. You then get a result of the aggregation - the number of system calls per process over the time in question.
I'm a neat freak, A couple of seconds plus or minus a half a second is useless to me, I crave precision. That's why the tick provider is so cool.
Say I want a trace to run for 5 seconds, I add 'tick-5sec { exit(0) }' to the end of my script or command and after 5 seconds all the gathered data is output.
you can simply profile what a system is doing by 'tick-97hz { @[stack()] = count() }', which shows what happens in line with the clock.
That's not all, you can output data points every 'tick' intervals, so for example if you are gathering the system call information, and want to output the call count every 5 seconds you can do: 'syscall:::entry { @[probefunc] = count() } tick-5sec { printa(@); cleara(@); }', which gives you the system call count every 5 seconds - just like iostat would give you the io count every 5 seconds or mpstat would give you the processor information every 5 seconds.... Easily accomplished in a few lines.
Dtrace... it slices, it dices, it makes coffee in the morning (and it will need to for me as it's 2am).
September 09, 2004 02:10 AM IST
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Preparation is the key
I have a shiney laptop, and I was planning on showing off a 64bit operating system running on it for my last dtrace presentation, so making sure I had the latest and greatest AMD64 bits, I started to prepare a few scripts that would allow me to show off what dtrace can do. I fired up one of my most complicated examples and bang my laptop rebooted.
It's just as well this was in my pre-flight test mode and not in front of everyone, because heaven knows, you don't need to have it all go horribly wrong in front of everyone.
As a preparation freak, I of course have the latest clean build of Solaris on an alternate boot environment on the laptop, so I quickly swapped unstable for stable to ensure that the demo went without a hitch.
Live upgrade, yet another reason why Solaris rules!
September 09, 2004 01:58 AM IST
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