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From: Artem Belevich <art@freebsd.org>
To: David Christensen <davidch@broadcom.com>
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Subject: Re: Using Dtrace for Performance Evaluation
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On Thu, May 5, 2011 at 4:33 PM, David Christensen <davidch@broadcom.com> wr=
ote:
>> > After building dtrace into the kernel and loading the dtraceall
>> > kernel module, when I load my bxe kernel module and run "dtrace -l"
>> > to list all supported probes I notice that many functions have an
>> > entry probe but no exit probe. =A0This effectively prevents me from
>> > calculating timestamps on "fbt:if_bxe::return" probes. =A0Why am I
>> > seeing this behavior?
>>
>> Tail call optimization could do that to you:
>> http://en.wikipedia.org/wiki/Tail_call
>
> How to disable tail call optimization when building my driver?

Google is your friend:

Either compile with -O0/-O1, or use -fno-optimize-sibling-calls.
http://stackoverflow.com/questions/3679435/how-do-i-disable-tailcall-optimi=
zations-in-gcc

--Artem