dtrace discuss - Feb 2006 - Dtrace probes for IRAF app I/O problem

hi all,

We are benchmarking an application called IRAF on Solaris on SPARC and 
X86 vs.  RHE.
under Solaris on both architechures the benchmark grinds to a halt on 
the I/O tasks, but the O/S doesn''t report anything untoward - iostat 
says the disc is fine and top seems i/o at 0.1%.

Running the same test on RHE on the same X86 box there is no problem 
with I/O.

Does anyone know how I can set-up dtrace to monitor the I/O and see what 
slows the application down, and where the application slows down?

I am new to dtrace (but not solaris), and hope that dtrace could shed 
some light.

Any replies would be grateful,
Simon.

-- 
// Nothing fancy and nothing Microsoft

On Fri, 24 Feb 2006, LOEWENTHAL Simon wrote:
> We are benchmarking an application called IRAF on Solaris on SPARC and X86 
> vs.  RHE. under Solaris on both architechures the benchmark grinds to a 
> halt on the I/O tasks, but the O/S doesn''t report anything
untoward -
> iostat says the disc is  fine and top seems i/o at 0.1%.
>
> Running the same test on RHE on the same X86 box there is no problem with 
> I/O.
>
> Does anyone know how I can set-up dtrace to monitor the I/O and see what 
> slows the application down, and where the application slows down?
Hi Simon,

How did you determine that this is an I/O problem? If this truly is an 
I/O problem, you might be interested in my SysAdmin article "Observing 
I/O Behavior with the DTraceToolkit":

http://www.samag.com/documents/s=9915/sam0512a/0512a.htm

The article covers several scripts in the DTraceToolkit (e.g., rwtop, 
rwsnoop, iosnoop,iotop, iopattern, etc.) that can be used to view 
application I/O characteristics. If you can provide a bit more detail, I 
am sure the list can help you DTrace a solution.

Thanks,
- Ryan
--
UNIX Administrator
http://daemons.net/~matty