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Date: Tue, 16 Apr 2013 16:03:06 -0400
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Subject: Re: DTrace gone quiet?
From: Ryan Stone <rysto32@gmail.com>
To: Navdeep Parhar <np@freebsd.org>
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On Tue, Apr 16, 2013 at 3:57 PM, Navdeep Parhar <np@freebsd.org> wrote:

> I just upgraded my kernel and userspace to head (r249552) and I notice
> that DTrace doesn't output anything until I hit ctrl-c.  All previous
> "hits" on the probe appear lost.  For example:
>
> # dtrace -n 'fbt::ether_output:entry'
> dtrace: description 'fbt::ether_output:entry' matched 1 probe
>
> (No output here.  I waited a long time before the ctrl-c and I know the
> system is actively transmitting and receiving Ethernet traffic).
>
> ^C
> CPU     ID                    FUNCTION:NAME
>   9  29354               ether_output:entry
>   8  29354               ether_output:entry
>   8  29354               ether_output:entry
>   8  29354               ether_output:entry
>
>
> Can anyone confirm or contradict this on a recent HEAD (around r249552
> in my case)?
>
> Regards,
> Navdeep
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>

Hm, if you run with "-x bufpolicy=switch" does it work?  It sounds as
through the ring buffer policy is being set by default for you.  I'm not
sure how that could happen.