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From: John Baldwin <jhb@freebsd.org>
To: Andrey Zonov <andrey@zonov.org>
Date: Wed, 11 Apr 2012 12:02:05 -0400
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
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Subject: Re: svn commit: r233925 - in head: sys/kern sys/sys sys/vm
	usr.bin/kdump usr.bin/ktrace
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On Tuesday, April 10, 2012 3:47:23 pm Andrey Zonov wrote:
> On 05.04.2012 21:13, John Baldwin wrote:
> > Author: jhb
> > Date: Thu Apr  5 17:13:14 2012
> > New Revision: 233925
> > URL: http://svn.freebsd.org/changeset/base/233925
> >
> > Log:
> >    Add new ktrace records for the start and end of VM faults.  This gives
> >    a pair of records similar to syscall entry and return that a user can
> >    use to determine how long page faults take.  The new ktrace records are
> >    enabled via the 'p' trace type, and are enabled in the default set of
> >    trace points.
> >
> >    Reviewed by:	kib
> >    MFC after:	2 weeks
> >
> 
> Hi John,
> 
> Thanks a lot, this change is very useful!
> 
> And while you are here I would like to show you a patch which adds a 
> "wmesg" to the context switch tracing.  It is not finished, it's just a 
> concept.  Please review it and if you are interesting in that I'll 
> finish it and will test more widely.

Ah, this looks fairly neat.  However, I think you will need a few changes:

1) You will want to make kdump handle either the old or new size of struct
ktr_csw.  (The size of the record is in the header, so as long as you have
a 'struct ktr_csw_old' you can handle this fairly easily.)

2) cs->wmesg is never NULL.  Instead, it should probably just always print it 
out.

3) condvar's have a valid wmesg.

-- 
John Baldwin