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Message-Id: <4F4788A50200007800074A26@nat28.tlf.novell.com> Date: Fri, 24 Feb 2012 11:55:01 +0000 From: "Jan Beulich" <JBeulich@...e.com> To: <mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com> Cc: <ak@...ux.intel.com>, <linux-kernel@...r.kernel.org> Subject: [PATCH, resend] x86-64: improve insn scheduling in SAVE_ARGS_IRQ In one case, use an address register that was computed earlier (and with a simpler instruction), thus reducing the risk of a stall. In the second case, eliminate a branch by using a conditional move (as is already done in call_softirq and xen_do_hypervisor_callback). Signed-off-by: Jan Beulich <jbeulich@...e.com> Reviewed-by: Andi Kleen <ak@...ux.intel.com> --- arch/x86/kernel/entry_64.S | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) --- 3.3-rc4/arch/x86/kernel/entry_64.S +++ 3.3-rc4-x86_64-entry-sched/arch/x86/kernel/entry_64.S @@ -320,7 +320,7 @@ ENDPROC(native_usergs_sysret64) movq %rsp, %rsi leaq -RBP(%rsp),%rdi /* arg1 for handler */ - testl $3, CS(%rdi) + testl $3, CS-RBP(%rsi) je 1f SWAPGS /* @@ -330,11 +330,10 @@ ENDPROC(native_usergs_sysret64) * moving irq_enter into assembly, which would be too much work) */ 1: incl PER_CPU_VAR(irq_count) - jne 2f - mov PER_CPU_VAR(irq_stack_ptr),%rsp + cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp CFI_DEF_CFA_REGISTER rsi -2: /* Store previous stack value */ + /* Store previous stack value */ pushq %rsi CFI_ESCAPE 0x0f /* DW_CFA_def_cfa_expression */, 6, \ 0x77 /* DW_OP_breg7 */, 0, \ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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