Date: Mon, 29 Feb 2016 14:20:04 -0800 From: Mark Johnston <markj@FreeBSD.org> To: hiren panchasara <hiren@strugglingcoder.info> Cc: sbruno@FreeBSD.org, freebsd-dtrace@freebsd.org Subject: Re: Functions not getting picked up by dtrace Message-ID: <20160229222004.GB67805@wkstn-mjohnston.west.isilon.com> In-Reply-To: <20160229220745.GG82027@strugglingcoder.info> References: <20160229213933.GE82027@strugglingcoder.info> <20160229214910.GA67805@wkstn-mjohnston.west.isilon.com> <20160229214923.GF82027@strugglingcoder.info> <20160229220745.GG82027@strugglingcoder.info>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, Feb 29, 2016 at 02:07:45PM -0800, hiren panchasara wrote: > On 02/29/16 at 01:49P, hiren panchasara wrote: > > On 02/29/16 at 01:49P, Mark Johnston wrote: > > > On Mon, Feb 29, 2016 at 01:39:33PM -0800, hiren panchasara wrote: > > > > I've seen this earlier with others too but this one is the latest > > > > confusing me: em_xmit() in $src/dev/e1000/if_em.c > > > > > > > > Other functions with similar signature are listed in 'dtrace -l'. > > > > > > em_xmit() is a static function with a single call site, so it's getting > > > inlined into its caller. DTrace FBT can't instrument inlined functions. > > > > > > > > > > > Is is because of some optimization? How do I undo it for testing > > > > purposes? > > > > > > There's a __noinline attribute that you can use for this. > > > > Thanks, Mark. > > > > cem on irc also explained the "why" part. > > Davide pointed out that it _might_ be possible that compiler change the > way it decides what to inline and non-static functions can also get > hidden that way from dtrace. Indeed: the compiler may inline a copy of a non-static function at call sites in the same compilation unit as the definition of the function. This case is more insidious since a fbt:::entry probe will exist for the function, and the only way to determine whether the function was inlined at a given call site is by examining the disassembly.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20160229222004.GB67805>