This is the mail archive of the systemtap@sourceware.org mailing list for the systemtap project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: A blktrace tapset, or 101 things you can do with blktrace and systemtap


On Mon, 2007-03-05 at 12:59 -0500, Frank Ch. Eigler wrote:
> Tom Zanussi <zanussi@comcast.net> writes:

> > # stap -I tapsets countall.stp
> > # btrace /dev/hda
> 
> Is there some way for the systemtap script to perform the tracing
> activation done by the btrace tool?

AFAIK, there's no API in blktrace that would allow the runtime to easily
toggle tracing on/off from the kernel side.  It would probably take just
a couple lines of code to add something that would do it, but that would
also add a couple to tests to the logging path, which I doubt would be
acceptable.  So probably best to just have a shell script that starts
the systemtap script and also starts blktrace.  Personally I don't find
it too onerous to start blktrace manually, but I'm guessing you might
have other possibilities in mind for solving this problem. ;-)

> 
> > [...] This script needs a couple extra changes to the normal commandline, so
> > it doesn't choke on some default systemtap limits:
> > # stap -I tapsets -DMAXMAPENTRIES=10000 -DMAXACTION=10000 iotop.stp
> > [...]
> 
> In what cases would your script come up against the MAXACTION limits?

I probably just kept this command-line from previous tests where it did
matter - I often use these defensively in order to avoid having a
long-running script run to completion only to choke at the end when
printing the results.

Tom




Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]