linuxppc-dev.lists.ozlabs.org archive mirror
 help / color / mirror / Atom feed
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: linuxppc-dev@ozlabs.org, Steven Rostedt <srostedt@redhat.com>,
	Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ftrace: On PowerPC we don't need frame pointers for CALLER_ADDRs
Date: Mon, 02 Feb 2009 11:35:19 +1100	[thread overview]
Message-ID: <1233534919.18767.69.camel@pasglop> (raw)
In-Reply-To: <20090131190650.GA4284@oksana.dev.rtsoft.ru>

On Sat, 2009-01-31 at 22:06 +0300, Anton Vorontsov wrote:
> According to this discussion:
> 
> http://lkml.org/lkml/2008/7/25/338
> http://lkml.org/lkml/2008/7/26/72
> 
> Frame pointers do nothing useful on PowerPC, so lib/Kconfig.debug
> makes CONFIG_FRAME_POINTER unselectable on PPC targets. But ftrace.h
> requires CONFIG_FRAME_POINTER for CALLER_ADDR macros. Therefore
> tracing is completely useless on PowerPC:

But we need them for -pg which ftrace uses no ? (ie, gcc forces you to
have -fno-omit-frame-pointers with -fpg iirc).

Now, regardless, I agree that on PPC, __builtin_return_address() should
always work with our without that cruft, so we may as well apply that
patch...

> [...]
>   <idle>-0       0X.h3    2us+:      0:140:R   + [000]  1733:120:S mvtsd
>   <idle>-0       0X.h3    9us+: 0 (0)
>   <idle>-0       0X..3   72us : 0 (0)
>   <idle>-0       0X..3   73us :      0:140:R ==> [000]  1733:120:R mvtsd
> 
> On PPC we can safely use __builtin_return_address(1..6) w/o frame
> pointers, and with this patch the trace output looks OK:
> 
> [...]
>   <idle>-0       0X.h3    2us+:      0:140:R   + [000]  1740:120:S mvtsd
>   <idle>-0       0X.h3    9us+: hrtimer_wakeup (__run_hrtimer)
>   <idle>-0       0X..3   87us : cpu_idle (__got2_end)
>   <idle>-0       0X..3   89us :      0:140:R ==> [000]  1740:120:R mvtsd
> 
> Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
> ---
> 
> Btw, on PowerPC tracing is also broken w/o "ring-buffer: fix alignment
> problem" patch (currently collecting dust in the -tip tree, commit
> 082605de5f82eb692cc90f7fda071cc01bb5ac34). Any chance the fix go into
> Linus' tree, to not waste other people's time bisecting and debugging
> the problem? ;-)
> 
> For google: tracing, regression, "ring-buffer: move some metadata
> into buffer page", commit abc9b56d66fbd4d93302ef4bf6fa726e1b8255f9,
> answer is here.
> 
>  include/linux/ftrace.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 9c5bc6b..13eba02 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -146,7 +146,7 @@ static inline void __ftrace_enabled_restore(int enabled)
>  #endif
>  }
>  
> -#ifdef CONFIG_FRAME_POINTER
> +#if defined(CONFIG_FRAME_POINTER) || defined(CONFIG_PPC)
>  /* TODO: need to fix this for ARM */
>  # define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
>  # define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))

  reply	other threads:[~2009-02-02  0:35 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-01-31 19:06 [PATCH] ftrace: On PowerPC we don't need frame pointers for CALLER_ADDRs Anton Vorontsov
2009-02-02  0:35 ` Benjamin Herrenschmidt [this message]
2009-02-02 14:04   ` Steven Rostedt
2009-02-03 14:56     ` [PATCH v2] " Anton Vorontsov
2009-02-03 16:06       ` Ingo Molnar
2009-02-03 16:19         ` Anton Vorontsov
2009-02-03 16:32           ` Steven Rostedt
2009-02-03 18:59             ` Anton Vorontsov
2009-02-04  0:34               ` Benjamin Herrenschmidt
2009-02-04 15:07           ` Anton Vorontsov
2009-02-04 15:08             ` [PATCH 1/3] Makefile: Include arch Makefiles as late as possible Anton Vorontsov
2009-02-04 21:26               ` Ingo Molnar
2009-02-11  3:51                 ` Benjamin Herrenschmidt
2009-02-11 13:23                   ` Ingo Molnar
2009-02-11 14:11                     ` Steven Rostedt
2009-02-14 19:58                   ` Sam Ravnborg
2009-02-14 19:57                 ` Sam Ravnborg
2009-02-14 22:03                   ` Ingo Molnar
2009-02-15  0:19                     ` Benjamin Herrenschmidt
2009-02-15  8:09                       ` Ingo Molnar
2009-02-16 14:20                   ` Anton Vorontsov
2009-02-16 14:53                     ` Anton Vorontsov
2009-02-16 20:04                       ` Sam Ravnborg
2009-02-16 16:08                     ` Anton Vorontsov
2009-02-16 17:22                       ` Ingo Molnar
2009-02-04 15:08             ` [PATCH 2/3] powerpc: Make it possible to safely select CONFIG_FRAME_POINTER Anton Vorontsov
2009-02-05  0:31               ` Benjamin Herrenschmidt
2009-02-05  0:35                 ` Steven Rostedt
2009-02-05  1:12                   ` Anton Vorontsov
2009-02-05  1:15                   ` Benjamin Herrenschmidt
2009-02-05  1:30                     ` Anton Vorontsov
2009-02-05 15:45                       ` Anton Vorontsov
2009-02-04 15:08             ` [PATCH 3/3] tracing: Tracers that use CALLER_ADDR macros should select FRAME_POINTER Anton Vorontsov
2009-02-04 15:26               ` Frédéric Weisbecker
2009-02-04 15:31                 ` Steven Rostedt
2009-02-04 15:36                 ` Anton Vorontsov
2009-02-04 16:50                   ` Frédéric Weisbecker
2009-02-04  8:17       ` [PATCH v2] ftrace: On PowerPC we don't need frame pointers forCALLER_ADDRs Usha Rani Konudula
2009-02-04  8:37         ` Usha Rani Konudula

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=1233534919.18767.69.camel@pasglop \
    --to=benh@kernel.crashing.org \
    --cc=avorontsov@ru.mvista.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linuxppc-dev@ozlabs.org \
    --cc=mingo@elte.hu \
    --cc=paulus@samba.org \
    --cc=srostedt@redhat.com \
    /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 NNTP newsgroup(s).