Date: Sun, 10 Jun 2012 16:40:52 -0400 From: Ryan Stone <rysto32@gmail.com> To: Andriy Gapon <avg@freebsd.org> Cc: freebsd-hackers@freebsd.org, Fabian Keil <freebsd-listen@fabiankeil.de> Subject: Re: decoding of multi-byte nops in dtrace Message-ID: <CAFMmRNwURMy55acPGZfYWnNSCB8VUvqWExV27RhBqcZHVUY==A@mail.gmail.com> In-Reply-To: <4FD4CD8B.1080803@FreeBSD.org> References: <4FD490D5.1070207@FreeBSD.org> <20120610152721.3b627896@fabiankeil.de> <4FD4CD8B.1080803@FreeBSD.org>
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On Sun, Jun 10, 2012 at 12:38 PM, Andriy Gapon <avg@freebsd.org> wrote: > Interesting observations, thank you. > Do you use -O2 or higher optimization for kernel/modules build? > I use only -O1. > > Here are some stats from my system: > $ dtrace -ln fbt::: | fgrep -c entry > 16876 > $ dtrace -ln fbt::: | fgrep -c return > 16729 > > So, 147 functions without return probe. Try re-compiling with -foptimize-sibling-calls. That enables the tail call optimization in gcc, and therefore you get many functions with no ret instruction (and thus no return probe in DTrace)
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