From: "Jan Beulich" <JBeulich@novell.com>
To: <mingo@elte.hu>, <tglx@linutronix.de>, <hpa@zytor.com>
Cc: <linux-kernel@vger.kernel.org>
Subject: [PATCH] x86-64: adjust ia32entry branches for better static prediction
Date: Tue, 20 Oct 2009 08:10:04 +0100 [thread overview]
Message-ID: <4ADD7E6C020000780001AD73@vpn.id2.novell.com> (raw)
Swap branch pairs so that the static branch prediction logic would
consider the syscall-number-in-range case the taken path.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
---
arch/x86/ia32/ia32entry.S | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
--- linux-2.6.32-rc5/arch/x86/ia32/ia32entry.S 2009-10-19 13:12:43.000000000 +0200
+++ 2.6.32-rc5-x86_64-ia32-syscall-trace-branch-dir/arch/x86/ia32/ia32entry.S 2009-10-19 09:36:39.000000000 +0200
@@ -249,9 +249,9 @@ sysenter_tracesys:
call syscall_trace_enter
LOAD_ARGS32 ARGOFFSET /* reload args from stack in case ptrace changed it */
RESTORE_REST
- cmpl $(IA32_NR_syscalls-1),%eax
- ja int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */
- jmp sysenter_do_call
+ cmpl $IA32_NR_syscalls,%eax
+ jb sysenter_do_call
+ jmp int_ret_from_sys_call /* sysenter_tracesys has set RAX(%rsp) */
CFI_ENDPROC
ENDPROC(ia32_sysenter_target)
@@ -368,9 +368,9 @@ cstar_tracesys:
LOAD_ARGS32 ARGOFFSET, 1 /* reload args from stack in case ptrace changed it */
RESTORE_REST
xchgl %ebp,%r9d
- cmpl $(IA32_NR_syscalls-1),%eax
- ja int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */
- jmp cstar_do_call
+ cmpl $IA32_NR_syscalls,%eax
+ jb cstar_do_call
+ jmp int_ret_from_sys_call /* cstar_tracesys has set RAX(%rsp) */
END(ia32_cstar_target)
ia32_badarg:
@@ -445,9 +445,9 @@ ia32_tracesys:
call syscall_trace_enter
LOAD_ARGS32 ARGOFFSET /* reload args from stack in case ptrace changed it */
RESTORE_REST
- cmpl $(IA32_NR_syscalls-1),%eax
- ja int_ret_from_sys_call /* ia32_tracesys has set RAX(%rsp) */
- jmp ia32_do_call
+ cmpl $IA32_NR_syscalls,%eax
+ jb ia32_do_call
+ jmp int_ret_from_sys_call /* ia32_tracesys has set RAX(%rsp) */
END(ia32_syscall)
ia32_badsys:
next reply other threads:[~2009-10-20 7:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-20 7:10 Jan Beulich [this message]
2009-10-20 7:21 ` Eric Dumazet
2009-10-20 7:24 ` H. Peter Anvin
2009-10-26 8:28 ` Andi Kleen
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