Date: Mon, 11 Jun 2012 00:24:45 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Ryan Stone <rysto32@gmail.com> Cc: freebsd-hackers@FreeBSD.org, Fabian Keil <freebsd-listen@fabiankeil.de> Subject: Re: decoding of multi-byte nops in dtrace Message-ID: <4FD5109D.5090107@FreeBSD.org> In-Reply-To: <CAFMmRNwURMy55acPGZfYWnNSCB8VUvqWExV27RhBqcZHVUY==A@mail.gmail.com> References: <4FD490D5.1070207@FreeBSD.org> <20120610152721.3b627896@fabiankeil.de> <4FD4CD8B.1080803@FreeBSD.org> <CAFMmRNwURMy55acPGZfYWnNSCB8VUvqWExV27RhBqcZHVUY==A@mail.gmail.com>
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on 10/06/2012 23:40 Ryan Stone said the following: > 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) No, thank you :-) I switched from -O2 to -O1 exactly for this reason (among a few others), although -fno-optimize-sibling-calls would be a more targeted solution. -- Andriy Gapon
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