From: Steven Rostedt <rostedt@goodmis.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Richard Guenther <richard.guenther@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
feng.tang@intel.com, Fr??d??ric Weisbecker <fweisbec@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
jakub@redhat.com, gcc@gcc.gnu.org
Subject: Re: BUG: GCC-4.4.x changes the function frame on some functions
Date: Thu, 19 Nov 2009 19:08:00 -0000 [thread overview]
Message-ID: <1258657614.22249.824.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <20091119184716.GA25458@elte.hu>
On Thu, 2009-11-19 at 19:47 +0100, Ingo Molnar wrote:
> * Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> > Admittedly, anybody who compiles with -pg probably doesn't care deeply
> > about smaller and more efficient code, since the mcount call overhead
> > tends to make the thing moot anyway, but it really looks like a
> > win-win situation to just fix the mcount call sequence regardless.
>
> Just a sidenote: due to dyn-ftrace, which patches out all mcounts during
> bootup to be NOPs (and opt-in patches them in again if someone runs the
> function tracer), the cost is not as large as one would have it with say
> -pg based user-space profiling.
>
> It's not completely zero-cost as the pure NOPs balloon the i$ footprint
> a bit and GCC generates different code too in some cases. But it's
> certainly good enough that it's generally pretty hard to prove overhead
> via micro or macro benchmarks that the patched out mcounts call sites
> are there.
And frame pointers do add a little overhead as well. Too bad the mcount
ABI wasn't something like this:
<function>:
call mcount
[...]
This way, the function address for mcount would have been (%esp) and the
parent address would be 4(%esp). Mcount would work without frame
pointers and this whole mess would also become moot.
-- Steve
next prev parent reply other threads:[~2009-11-19 19:08 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <alpine.LFD.2.00.0911181933540.24119@localhost.localdomain>
[not found] ` <tip-887a29f59b93cf54e21814869a4ab6e80b6fa623@git.kernel.org>
[not found] ` <20091119072040.GA23579@elte.hu>
[not found] ` <alpine.LFD.2.00.0911191053390.24119@localhost.localdomain>
[not found] ` <alpine.LFD.2.00.0911191423190.24119@localhost.localdomain>
2009-11-19 15:39 ` Thomas Gleixner
2009-11-19 15:45 ` Andrew Haley
2009-11-19 15:55 ` H. Peter Anvin
2009-11-19 15:59 ` Richard Guenther
2009-11-19 16:03 ` Steven Rostedt
2009-11-19 16:13 ` H. Peter Anvin
2009-11-19 16:20 ` Frederic Weisbecker
2009-11-19 16:07 ` Thomas Gleixner
2009-11-19 16:19 ` Andrew Haley
2009-11-19 16:45 ` Thomas Gleixner
2009-11-19 16:13 ` Steven Rostedt
2009-11-19 15:46 ` H. Peter Anvin
2009-11-19 15:51 ` Richard Guenther
2009-11-19 15:53 ` Richard Guenther
2009-11-19 17:38 ` Andi Kleen
2009-11-19 17:41 ` Linus Torvalds
2009-11-19 17:52 ` Thomas Gleixner
2009-11-19 18:00 ` Steven Rostedt
2009-11-19 18:04 ` Richard Guenther
2009-11-19 18:23 ` Andrew Haley
2009-11-19 18:42 ` Linus Torvalds
2009-11-19 18:45 ` Linus Torvalds
2009-11-19 18:56 ` Linus Torvalds
2009-11-19 19:03 ` Thomas Gleixner
2009-11-23 9:17 ` Jakub Jelinek
2009-11-23 9:53 ` Thomas Gleixner
2009-11-19 19:12 ` David Daney
2009-11-19 19:29 ` Steven Rostedt
2009-11-19 19:47 ` Frederic Weisbecker
2009-11-19 19:55 ` Kai Tietz
2009-11-19 20:06 ` Frederic Weisbecker
2009-11-19 20:06 ` Steven Rostedt
2009-11-19 20:18 ` Steven Rostedt
2009-11-19 20:29 ` Frederic Weisbecker
2009-11-19 20:26 ` Frederic Weisbecker
2009-11-19 20:38 ` Linus Torvalds
2009-11-19 20:45 ` Steven Rostedt
2009-11-19 19:51 ` H. Peter Anvin
2009-11-19 20:08 ` Linus Torvalds
2009-11-19 21:13 ` Jeff Law
2009-11-19 20:11 ` Steven Rostedt
2009-11-19 21:07 ` Jeff Law
2009-11-19 18:34 ` Thomas Gleixner
2009-11-19 18:40 ` Linus Torvalds
2009-11-19 18:48 ` Ingo Molnar
2009-11-19 19:08 ` Steven Rostedt [this message]
2009-11-19 19:51 ` Ingo Molnar
2009-11-20 9:58 ` [PATCH] gcc mcount-nofp was " Andi Kleen
2009-11-20 12:35 ` Steven Rostedt
2009-11-20 19:08 ` H. Peter Anvin
2009-11-19 20:37 ` Thomas Gleixner
2009-11-19 18:22 ` Andrew Haley
2009-11-19 18:34 ` Steven Rostedt
2009-11-19 18:37 ` Andrew Pinski
2009-11-19 18:38 ` Andrew Haley
2009-11-19 18:38 ` H. Peter Anvin
2009-11-19 18:40 ` Thomas Gleixner
2009-11-20 5:24 ` [PATCH][GIT PULL][v2.6.32] tracing/x86: Add check to detect GCC messing with mcount prologue Steven Rostedt
2009-11-20 5:33 ` Steven Rostedt
2009-11-20 17:02 ` Steven Rostedt
2009-11-20 17:15 ` H. Peter Anvin
2009-11-20 19:36 ` Andrew Haley
2009-11-20 19:48 ` Steven Rostedt
2009-11-20 19:50 ` H. Peter Anvin
2009-11-22 9:39 ` H.J. Lu
2009-11-22 17:21 ` Andrew Haley
2009-11-22 23:31 ` H.J. Lu
2009-11-24 14:43 ` Andrew Haley
2009-11-24 14:56 ` Thomas Gleixner
2009-11-24 15:06 ` Jakub Jelinek
2009-11-24 15:32 ` Andrew Haley
2009-11-24 15:36 ` Jakub Jelinek
2009-11-24 15:48 ` Andrew Haley
2009-11-24 16:39 ` H. Peter Anvin
2009-11-24 17:12 ` Andrew Haley
2009-11-24 17:30 ` Steven Rostedt
2009-11-25 20:05 ` H. Peter Anvin
2009-11-24 19:56 ` H. Peter Anvin
2009-11-25 15:29 ` Thomas Gleixner
2009-11-25 15:45 ` Ingo Molnar
2009-11-25 15:53 ` Thomas Gleixner
2009-11-25 16:26 ` Ingo Molnar
2009-11-25 16:45 ` Jakub Jelinek
2009-11-25 20:13 ` H. Peter Anvin
2009-11-25 21:01 ` Andrew Haley
2009-11-22 9:06 ` Ingo Molnar
2009-11-19 21:16 BUG: GCC-4.4.x changes the function frame on some functions H. Peter Anvin
2009-11-19 21:26 ` Jeff Law
2009-11-19 22:44 ` Steven Rostedt
2009-11-20 0:00 ` Jeff Law
2009-11-20 0:37 ` Thomas Gleixner
2009-11-20 1:00 ` Linus Torvalds
2009-11-20 1:29 ` Thomas Gleixner
2009-11-20 2:16 ` Thomas Gleixner
2009-11-20 1:30 ` H. Peter Anvin
2009-11-20 5:40 ` Ingo Molnar
2009-11-20 12:06 ` Andrew Haley
2009-11-20 12:23 ` Andrew Haley
-- strict thread matches above, loose matches on Subject: below --
2009-11-19 20:50 H. Peter Anvin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1258657614.22249.824.camel@gandalf.stny.rr.com \
--to=rostedt@goodmis.org \
--cc=akpm@linux-foundation.org \
--cc=feng.tang@intel.com \
--cc=fweisbec@gmail.com \
--cc=gcc@gcc.gnu.org \
--cc=heiko.carstens@de.ibm.com \
--cc=hpa@zytor.com \
--cc=jakub@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=peterz@infradead.org \
--cc=richard.guenther@gmail.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).