Date: Thu, 5 May 2011 16:43:53 -0700 From: Artem Belevich <art@freebsd.org> To: David Christensen <davidch@broadcom.com> Cc: "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Subject: Re: Using Dtrace for Performance Evaluation Message-ID: <BANLkTi=BLC=0udM9bX5zzT=bK1t%2BL9sm5Q@mail.gmail.com> In-Reply-To: <5D267A3F22FD854F8F48B3D2B523819360D799A517@IRVEXCHCCR01.corp.ad.broadcom.com> References: <5D267A3F22FD854F8F48B3D2B523819360D799A42B@IRVEXCHCCR01.corp.ad.broadcom.com> <BANLkTin0HxinK9e5w1VDsrse_L1xSEEW5g@mail.gmail.com> <5D267A3F22FD854F8F48B3D2B523819360D799A517@IRVEXCHCCR01.corp.ad.broadcom.com>
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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
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