From: David Mosberger-Tang Date: Mon, 25 Apr 2005 20:03:16 +0000 (-0700) Subject: [IA64] speed up syscall path a bit more X-Git-Tag: v2.6.12-rc4~197^2~27 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=30325d17715302a60c9afdaacaafaeb056b7e880;p=linux-2.6 [IA64] speed up syscall path a bit more Recently I noticed that clearing ar.ssd/ar.csd right before srlz.d is causing significant stalling in the syscall path. The patch below fixes that by moving the register-writes after srlz.d. On a Madison, this drops break-based getpid() from 241 to 226 cycles (-15 cycles). Signed-off-by: David Mosberger-Tang Signed-off-by: Tony Luck --- diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S index 0272c010a3..73e23dafe8 100644 --- a/arch/ia64/kernel/entry.S +++ b/arch/ia64/kernel/entry.S @@ -728,12 +728,8 @@ ENTRY(ia64_leave_syscall) mov f8=f0 // clear f8 ;; ld8 r30=[r2],16 // M0|1 load cr.ifs - mov.m ar.ssd=r0 // M2 clear ar.ssd - cmp.eq p9,p0=r0,r0 // set p9 to indicate that we should restore cr.ifs - ;; ld8 r25=[r3],16 // M0|1 load ar.unat - mov.m ar.csd=r0 // M2 clear ar.csd - mov r22=r0 // clear r22 + cmp.eq p9,p0=r0,r0 // set p9 to indicate that we should restore cr.ifs ;; ld8 r26=[r2],PT(B0)-PT(AR_PFS) // M0|1 load ar.pfs (pKStk) mov r22=psr // M2 read PSR now that interrupts are disabled @@ -756,11 +752,15 @@ ENTRY(ia64_leave_syscall) mov f7=f0 // clear f7 ;; ld8.fill r12=[r2] // restore r12 (sp) + mov.m ar.ssd=r0 // M2 clear ar.ssd + mov r22=r0 // clear r22 + ld8.fill r15=[r3] // restore r15 +(pUStk) st1 [r14]=r17 addl r3=THIS_CPU(ia64_phys_stacked_size_p8),r0 ;; (pUStk) ld4 r3=[r3] // r3 = cpu_data->phys_stacked_size_p8 -(pUStk) st1 [r14]=r17 + mov.m ar.csd=r0 // M2 clear ar.csd mov b6=r18 // I0 restore b6 ;; mov r14=r0 // clear r14