Adding new option to ktrace

[Nikhil Dharashivkar]

Yes, it is ok if i loose data in ktrace queue when crash occurs.
Basically,  I want to give an Disk IO trace support to ktrace on
FreeBSD.
       So, what  I am thinking to use struct dio  in dastrategy
routine to trace the IO.
I 'll use this struct to generate ktr_request. Throught
ktr_writerequest it will be written in ktrace.out .
      Is it possible ?



On 9/6/05, Peter Jeremy <PeterJeremy at optushome.com.au> wrote:
> On Tue, 2005-Sep-06 10:33:53 +0530, Nikhil Dharashivkar wrote:
> >     Thanks for replying me. Basically what happend, while testing
> >scsi driver on freebsd, at  some point it crashes. So, there is no way
> >to know how much IO is performed. To know the IO state just before the
> >driver fails, i selected ktrace to print IO information whatever i ll
> >get from dastrategy routine.
> 
> It's not clear how ktrace is going to help here.  The ktrXXX(9)
> functions place ktr_request events in a queue.  A kernel thread then
> dumps the queue entries into a file via the normal buffer cache.  The
> data on disk is typically about 30 seconds behind real time.  If the
> system crashes, you will lose any events that are still in the buffer
> cache or ktr_todo queue.
> 
> Another problem is that since ktrace generates disk I/O, it is likely
> to disturb your testing.
> 
> A better approach would seem to be to build a circular buffer and
> store the I/O requests in the buffer.  When the system crashes, you
> can look at the last entries in the buffer.
> 
> --
> Peter Jeremy
> 


-- 
Thanks and Regards,
         Nikhil.