Adding new option to ktrace

[Nikhil Dharashivkar]

Sorry it's struct bio instead of struct dio.

On 9/6/05, Nikhil Dharashivkar <nikhildharashivkar at gmail.com> wrote:
> 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.
> 


-- 
Thanks and Regards,
         Nikhil.