linux-kernel - [PATCH][GIT PULL] x86, function-graph: only save return values on x86

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Date:	Wed, 25 Mar 2009 16:27:29 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux kernel <linux-kernel@...r.kernel.org>
cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>, Tim Bird <tim.bird@...sony.com>,
	Ingo Molnar <mingo@...hat.com>,
	Abhishek Sagar <sagar.abhishek@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH][GIT PULL] x86, function-graph: only save return values on
 x86_64


Ingo,

Please pull the latest tip/tracing/function-graph tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/tracing/function-graph


Steven Rostedt (1):
      x86, function-graph: only save return values on x86_64

----
 arch/x86/kernel/entry_64.S |   19 +++----------------
 1 files changed, 3 insertions(+), 16 deletions(-)
---------------------------
commit d5b754b2208b1c22691a7cd5d1a65398b5973d74
Author: Steven Rostedt <srostedt@...hat.com>
Date:   Wed Mar 25 14:30:04 2009 -0400

    x86, function-graph: only save return values on x86_64
    
    Impact: speed up
    
    The return to handler portion of the function graph tracer should only
    need to save the return values. The caller already saved off the
    registers that the callee can modify. The returning function already
    saved the registers it modified. When we call our own trace function
    it too will save the registers that the callee must restore.
    
    There's no reason to save off anything more that the registers used
    to return the values.
    
    Note, I did a complete kernel build with this modification and the
    function graph tracer running on x86_64.
    
    Signed-off-by: Steven Rostedt <srostedt@...hat.com>

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index a331ec3..1ac9986 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -147,27 +147,14 @@ END(ftrace_graph_caller)
 GLOBAL(return_to_handler)
 	subq  $80, %rsp
 
+	/* Save the return values */
 	movq %rax, (%rsp)
-	movq %rcx, 8(%rsp)
-	movq %rdx, 16(%rsp)
-	movq %rsi, 24(%rsp)
-	movq %rdi, 32(%rsp)
-	movq %r8, 40(%rsp)
-	movq %r9, 48(%rsp)
-	movq %r10, 56(%rsp)
-	movq %r11, 64(%rsp)
+	movq %rdx, 8(%rsp)
 
 	call ftrace_return_to_handler
 
 	movq %rax, 72(%rsp)
-	movq 64(%rsp), %r11
-	movq 56(%rsp), %r10
-	movq 48(%rsp), %r9
-	movq 40(%rsp), %r8
-	movq 32(%rsp), %rdi
-	movq 24(%rsp), %rsi
-	movq 16(%rsp), %rdx
-	movq 8(%rsp), %rcx
+	movq 8(%rsp), %rdx
 	movq (%rsp), %rax
 	addq $72, %rsp
 	retq
--
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