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

["Frank Ch. Eigler" <fche at redhat dot com>]

Hi -

> > 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. [...]

One would have to simulate the BLKTRACE* ioctls.  Since a systemtap
script would absorb the tracing data during its creation, blktrace
proper could be told to keep only a negligible buffer for itself.

> > 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.

This issue keeps popping up.  We'll have to deal with it better sometime.

- FChE

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