[PATCH][GIT PULL] x86, function-graph: only save return values on x86_64

Steven Rostedt
2009-03-25T20:27:53Z

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@redhat.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@redhat.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