AuxXxilium/linux_dsm_epyc7002
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x86, function-graph: only save return values on x86_64

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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>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2009-03-25 14:30:04 -04:00 committed by Ingo Molnar
parent 2062501ae6
commit e71e99c294
1 changed files with 3 additions and 16 deletions
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19
arch/x86/kernel/entry_64.S
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@ -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