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authorDavid Mosberger-Tang <davidm@hpl.hp.com>2005-04-27 21:20:51 -0700
committerTony Luck <tony.luck@intel.com>2005-04-27 21:20:51 -0700
commit1ba7be7d691f6df2557d39c5b1a2e14c32e5dd20 (patch)
treef6c805c01be475f21de0cdcada8f69c9076ea61e /arch/ia64/kernel
parent21bc4f9b34cc1eab3610955207f72c52495ae8ed (diff)
[IA64] Reschedule fsys_bubble_down().
Improvements come from eliminating srlz.i, not scheduling AR/CR-reads too early (while there are others still pending), scheduling the backing-store switch as well as possible, splitting the BBB bundle into a MIB/MBB pair. Why is it safe to eliminate the srlz.i? Observe that we used to clear bits ~PSR_PRESERVED_BITS in PSR.L. Since PSR_PRESERVED_BITS==PSR.{UP,MFL,MFH,PK,DT,PP,SP,RT,IC}, we ended up clearing PSR.{BE,AC,I,DFL,DFH,DI,DB,SI,TB}. However, PSR.BE : already is turned off in __kernel_syscall_via_epc() PSR.AC : don't care (kernel normally turns PSR.AC on) PSR.I : already turned off by the time fsys_bubble_down gets invoked PSR.DFL: always 0 (kernel never turns it on) PSR.DFH: don't care --- kernel never touches f32-f127 on its own initiative PSR.DI : always 0 (kernel never turns it on) PSR.SI : always 0 (kernel never turns it on) PSR.DB : don't care --- kernel never enables kernel-level breakpoints PSR.TB : must be 0 already; if it wasn't zero on entry to __kernel_syscall_via_epc, the branch to fsys_bubble_down will trigger a taken branch; the taken-trap-handler then converts the syscall into a break-based system-call. In other words: all the bits we're clearying are either 0 already or are don't cares! Thus, we don't have to write PSR.L at all and we don't have to do a srlz.i either. Good for another ~20 cycle improvement for EPC-based heavy-weight syscalls. Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
Diffstat (limited to 'arch/ia64/kernel')
-rw-r--r--arch/ia64/kernel/fsys.S73
1 files changed, 33 insertions, 40 deletions
diff --git a/arch/ia64/kernel/fsys.S b/arch/ia64/kernel/fsys.S
index 0d8650f7fce..57c6556b1e0 100644
--- a/arch/ia64/kernel/fsys.S
+++ b/arch/ia64/kernel/fsys.S
@@ -549,9 +549,6 @@ GLOBAL_ENTRY(fsys_bubble_down)
* - r27: ar.rsc
* - r29: psr
*/
-# define PSR_PRESERVED_BITS (IA64_PSR_UP | IA64_PSR_MFL | IA64_PSR_MFH | IA64_PSR_PK \
- | IA64_PSR_DT | IA64_PSR_PP | IA64_PSR_SP | IA64_PSR_RT \
- | IA64_PSR_IC)
/*
* Reading psr.l gives us only bits 0-31, psr.it, and psr.mc. The rest we have
* to synthesize.
@@ -560,62 +557,58 @@ GLOBAL_ENTRY(fsys_bubble_down)
| IA64_PSR_BN | IA64_PSR_I)
invala
- movl r8=PSR_ONE_BITS
+ movl r14=ia64_ret_from_syscall
- mov r25=ar.unat // save ar.unat (5 cyc)
- movl r9=PSR_PRESERVED_BITS
-
- mov ar.rsc=0 // set enforced lazy mode, pl 0, little-endian, loadrs=0
+ nop.m 0
movl r28=__kernel_syscall_via_break
;;
- mov r23=ar.bspstore // save ar.bspstore (12 cyc)
- mov r31=pr // save pr (2 cyc)
- mov r20=r1 // save caller's gp in r20
- ;;
+
mov r2=r16 // copy current task addr to addl-addressable register
- and r9=r9,r29
- mov r19=b6 // save b6 (2 cyc)
+ adds r16=IA64_TASK_THREAD_ON_USTACK_OFFSET,r16
+ mov r31=pr // save pr (2 cyc)
;;
- mov psr.l=r9 // slam the door (17 cyc to srlz.i)
- or r29=r8,r29 // construct cr.ipsr value to save
+ st1 [r16]=r0 // clear current->thread.on_ustack flag
addl r22=IA64_RBS_OFFSET,r2 // compute base of RBS
+ add r3=TI_FLAGS+IA64_TASK_SIZE,r2
;;
- // GAS reports a spurious RAW hazard on the read of ar.rnat because it thinks
- // we may be reading ar.itc after writing to psr.l. Avoid that message with
- // this directive:
- dv_serialize_data
- mov.m r24=ar.rnat // read ar.rnat (5 cyc lat)
+ ld4 r3=[r3] // r2 = current_thread_info()->flags
lfetch.fault.excl.nt1 [r22]
- adds r16=IA64_TASK_THREAD_ON_USTACK_OFFSET,r2
-
- // ensure previous insn group is issued before we stall for srlz.i:
+ nop.i 0
;;
- srlz.i // ensure new psr.l has been established
- /////////////////////////////////////////////////////////////////////////////
- ////////// from this point on, execution is not interruptible anymore
- /////////////////////////////////////////////////////////////////////////////
- addl r1=IA64_STK_OFFSET-IA64_PT_REGS_SIZE,r2 // compute base of memory stack
- cmp.ne pKStk,pUStk=r0,r0 // set pKStk <- 0, pUStk <- 1
+ mov ar.rsc=0 // set enforced lazy mode, pl 0, little-endian, loadrs=0
+ nop.m 0
+ nop.i 0
+ ;;
+ mov r23=ar.bspstore // save ar.bspstore (12 cyc)
+ mov.m r24=ar.rnat // read ar.rnat (5 cyc lat)
+ nop.i 0
;;
- st1 [r16]=r0 // clear current->thread.on_ustack flag
mov ar.bspstore=r22 // switch to kernel RBS
- mov b6=r18 // copy syscall entry-point to b6 (7 cyc)
- add r3=TI_FLAGS+IA64_TASK_SIZE,r2
+ movl r8=PSR_ONE_BITS // X
;;
- ld4 r3=[r3] // r2 = current_thread_info()->flags
+ mov r25=ar.unat // save ar.unat (5 cyc)
+ mov r19=b6 // save b6 (2 cyc)
+ mov r20=r1 // save caller's gp in r20
+ ;;
+ or r29=r8,r29 // construct cr.ipsr value to save
+ mov b6=r18 // copy syscall entry-point to b6 (7 cyc)
+ addl r1=IA64_STK_OFFSET-IA64_PT_REGS_SIZE,r2 // compute base of memory stack
+
mov r18=ar.bsp // save (kernel) ar.bsp (12 cyc)
- mov ar.rsc=0x3 // set eager mode, pl 0, little-endian, loadrs=0
+ cmp.ne pKStk,pUStk=r0,r0 // set pKStk <- 0, pUStk <- 1
br.call.sptk.many b7=ia64_syscall_setup
;;
- ssm psr.i
- movl r2=ia64_ret_from_syscall
+ mov ar.rsc=0x3 // set eager mode, pl 0, little-endian, loadrs=0
+ mov rp=r14 // set the real return addr
+ nop.i 0
;;
- mov rp=r2 // set the real return addr
+ ssm psr.i
tbit.z p8,p0=r3,TIF_SYSCALL_TRACE
- ;;
(p10) br.cond.spnt.many ia64_ret_from_syscall // p10==true means out registers are more than 8
+
+ nop.m 0
(p8) br.call.sptk.many b6=b6 // ignore this return addr
- br.cond.sptk ia64_trace_syscall
+ br.cond.spnt ia64_trace_syscall
END(fsys_bubble_down)
.rodata