dtrace discuss - Jan 2006 - Understanding mpstat and vmstat with DTrace

Howdy,

I have been accumulating DTrace notes for the past few months, and wanted 
to stash them up on my website for easy access. I just finished writing a 
cheat sheet called "Understanding mpstat and vmstat with DTrace":

http://daemons.net/~matty/articles/dtracecookbook.html

I tend to use cheat sheets when I get called in the middle of the night to 
investigate problems (e.g., the system is slow). These help me transition 
my brain from happy relaxed mode to debugging mode. Not sure if folks will 
find this useful, but it''s there in case you want to reference it. I
would
LOVE to get feedback, comments and suggestions (especially if something is
wrong or worded poorly).

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

Hello Ryan,
>
> I have been accumulating DTrace notes for the past few months, and 
> wanted to stash them up on my website for easy access. I just finished 
> writing a cheat sheet called "Understanding mpstat and vmstat with 
> DTrace":
>
> http://daemons.net/~matty/articles/dtracecookbook.html
>
> I tend to use cheat sheets when I get called in the middle of the 
> night to investigate problems (e.g., the system is slow). These help 
> me transition my brain from happy relaxed mode to debugging mode. Not 
> sure if folks will find this useful, but it''s there in case you
want
> to reference it.
The article is very useful and interesting for that matter. It is the 
sort of thing that would be of interest to the people on the 
sysadmin-discuss and perf-discuss lists.
> I would
> LOVE to get feedback, comments and suggestions (especially if 
> something is
> wrong or worded poorly).
The only comment I would make is perhaps including a reference to some 
of the descriptions of the various metrics reported by the vmstat and 
mpstat tools. The Solaris Internals book is an excellent source of such 
information, albeit not freely available. That is perhaps beyond the 
scope of the article though.

An excellent article, I just wish the performance problem I am working 
on now was on a Solaris 10 system with DTrace.

Kind Regards,

Nathan Dietsch

> The only comment I would make is perhaps including a reference to some of
the
> descriptions of the various metrics reported by the vmstat and mpstat
tools.
> The Solaris Internals book is an excellent source of such information,
albeit
> not freely available. That is perhaps beyond the scope of the article
though.
I am working now to add hyper links to each mpstat/vmstat column (so 
clicking smtx will take you to the docs.sun.com description). I am also 
hoping to add iostat to the mix, since the DTraceToolkit and the io 
provider can help answer performance related questions.
> An excellent article, I just wish the performance problem I am working on
now
> was on a Solaris 10 system with DTrace.
I concur -- logging into a Solaris 7/8/9 box is just not the same anymore.

Thanks for the feedback!
- Ryan
--
UNIX Administrator
http://daemons.net/~matty

G''Day Folks,

On Wed, 25 Jan 2006, Matty wrote:
> > The only comment I would make is perhaps including a reference to some
of the
> > descriptions of the various metrics reported by the vmstat and mpstat
tools.
> > The Solaris Internals book is an excellent source of such information,
albeit
> > not freely available. That is perhaps beyond the scope of the article
though.
Agreed, or point them to the source code. If the article is intended for
senior admins / support, then such deeper resources are appropriate. For
the greater Solaris community, I think it could be argued that they
shouldn''t be learning every vmstat column anyway...
> I am working now to add hyper links to each mpstat/vmstat column (so
> clicking smtx will take you to the docs.sun.com description).
Oh boy, I''d like to see what you end up finding. ;)

I just had a quick look on the SOLARIS 10 docs on docs.sun.com. I found,

   http://docs.sun.com/app/docs/doc/817-0403/6mg741c5u?q=sar&a=view

   How to Check CPU Utilization (sar -u)
   [...]
   %wio
 	Lists the percentage of time that the processor is idle and
	waiting for I/O completion
   [...]
   A high %wio value generally means that a disk slowdown has occurred.

Alan!!???
> I am also
> hoping to add iostat to the mix, since the DTraceToolkit and the io
> provider can help answer performance related questions.
... and we have a resource that clearly documents what one of the I/O
metrics really means - www.brendangregg.com/Perf/solarismetrics.html :)

cheers,

Brendan

[Sydney, Australia]