diff options
| author | Anthony Yznaga <anthony.yznaga@oracle.com> | 2017-08-18 12:40:36 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-09-09 20:20:11 -0700 |
| commit | a7159a87a3836f61a97882e671d2d66bbb96c62e (patch) | |
| tree | 3f56de47be55b0367bb7588869f9c95ee2516409 /arch/sparc/kernel/etrap_64.S | |
| parent | 5bd0ea9107dca975dc4ba4d9de39b4938d2cb36d (diff) | |
sparc64: speed up etrap/rtrap on NG2 and later processors
For many sun4v processor types, reading or writing a privileged register
has a latency of 40 to 70 cycles. Use a combination of the low-latency
allclean, otherw, normalw, and nop instructions in etrap and rtrap to
replace 2 rdpr and 5 wrpr instructions and improve etrap/rtrap
performance. allclean, otherw, and normalw are available on NG2 and
later processors.
The average ticks to execute the flush windows trap ("ta 0x3") with and
without this patch on select platforms:
CPU Not patched Patched % Latency Reduction
NG2 1762 1558 -11.58
NG4 3619 3204 -11.47
M7 3015 2624 -12.97
SPARC64-X 829 770 -7.12
Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/sparc/kernel/etrap_64.S')
| -rw-r--r-- | arch/sparc/kernel/etrap_64.S | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/arch/sparc/kernel/etrap_64.S b/arch/sparc/kernel/etrap_64.S index 1276ca2567ba..5c237467d156 100644 --- a/arch/sparc/kernel/etrap_64.S +++ b/arch/sparc/kernel/etrap_64.S @@ -38,7 +38,11 @@ etrap_syscall: TRAP_LOAD_THREAD_REG(%g6, %g1) or %g1, %g3, %g1 bne,pn %xcc, 1f sub %sp, STACKFRAME_SZ+TRACEREG_SZ-STACK_BIAS, %g2 - wrpr %g0, 7, %cleanwin +661: wrpr %g0, 7, %cleanwin + .section .fast_win_ctrl_1insn_patch, "ax" + .word 661b + .word 0x85880000 ! allclean + .previous sethi %hi(TASK_REGOFF), %g2 sethi %hi(TSTATE_PEF), %g3 @@ -88,16 +92,30 @@ etrap_save: save %g2, -STACK_BIAS, %sp bne,pn %xcc, 3f mov PRIMARY_CONTEXT, %l4 - rdpr %canrestore, %g3 +661: rdpr %canrestore, %g3 + .section .fast_win_ctrl_1insn_patch, "ax" + .word 661b + nop + .previous + rdpr %wstate, %g2 - wrpr %g0, 0, %canrestore +661: wrpr %g0, 0, %canrestore + .section .fast_win_ctrl_1insn_patch, "ax" + .word 661b + nop + .previous sll %g2, 3, %g2 /* Set TI_SYS_FPDEPTH to 1 and clear TI_SYS_NOERROR. */ mov 1, %l5 sth %l5, [%l6 + TI_SYS_NOERROR] - wrpr %g3, 0, %otherwin +661: wrpr %g3, 0, %otherwin + .section .fast_win_ctrl_1insn_patch, "ax" + .word 661b + .word 0x87880000 ! otherw + .previous + wrpr %g2, 0, %wstate sethi %hi(sparc64_kern_pri_context), %g2 ldx [%g2 + %lo(sparc64_kern_pri_context)], %g3 |