[PATCH] Add ktrace records for user page faults

[John Baldwin]

On Tuesday, May 03, 2011 7:38:44 am Alexander Leidinger wrote:
> Quoting John Baldwin <jhb at freebsd.org> (from Mon, 2 May 2011 16:02:02 -0400):
> 
> > It is true that it would be nice to have the exact faulting address, though
> > having page granularity has been sufficient for the few times I've actually
> > used the address itself (e.g. I could figure out which page of libstdc++ a
> > fault occurred on and narrow down from there as to which of the routines most
> > likely was executed given what the app was doing at the time).  In my case
> > knowing how much time was spent handling a page fault has been useful.
> >
> > Would we have to push this logic out of vm_fault and into every  
> > trap() routine
> > to get the original address?  That would make the patch quite a bit bigger
> > (touching N MD files vs 1 MI file).
> 
> dtrace is not a solution here (in general, not to the exact-address problem)?

It probably is, but many folks are still quite used to ktrace.  At some point
I may sit down and spend more time with DTrace, but for now I have other fish
to fry.  I can just keep the page fault tracing patch private if that is what
folks prefer.

-- 
John Baldwin