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@xxxxxxxxxx>
---
v2:
Simplified and future-proofed changes to sun4v_patch()
by just skipping hot patching for Niagara1 processors.
---
arch/sparc/include/asm/trap_block.h | 2 ++
arch/sparc/kernel/etrap_64.S | 26 ++++++++++++++++++++++----
arch/sparc/kernel/rtrap_64.S | 13 +++++++++++--
arch/sparc/kernel/setup_64.c | 5 +++++
arch/sparc/kernel/vmlinux.lds.S | 5 +++++
5 files changed, 45 insertions(+), 6 deletions(-)
diff --git a/arch/sparc/include/asm/trap_block.h b/arch/sparc/include/asm/trap_block.h
index ff05992..dfc5386 100644
--- a/arch/sparc/include/asm/trap_block.h
+++ b/arch/sparc/include/asm/trap_block.h
@@ -73,6 +73,8 @@ struct sun4v_1insn_patch_entry {
};
extern struct sun4v_1insn_patch_entry __sun4v_1insn_patch,
__sun4v_1insn_patch_end;
+extern struct sun4v_1insn_patch_entry __fast_win_ctrl_1insn_patch,
+ __fast_win_ctrl_1insn_patch_end;
struct sun4v_2insn_patch_entry {
unsigned int addr;
diff --git a/arch/sparc/kernel/etrap_64.S b/arch/sparc/kernel/etrap_64.S
index 1276ca2..5c23746 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
diff --git a/arch/sparc/kernel/rtrap_64.S b/arch/sparc/kernel/rtrap_64.S
index 709a82e..dff86fa 100644
--- a/arch/sparc/kernel/rtrap_64.S
+++ b/arch/sparc/kernel/rtrap_64.S
@@ -224,10 +224,19 @@ rt_continue: ldx [%sp + PTREGS_OFF + PT_V9_G1], %g1
rdpr %otherwin, %l2
srl %l1, 3, %l1
- wrpr %l2, %g0, %canrestore
+661: wrpr %l2, %g0, %canrestore
+ .section .fast_win_ctrl_1insn_patch, "ax"
+ .word 661b
+ .word 0x89880000 ! normalw
+ .previous
+
wrpr %l1, %g0, %wstate
brnz,pt %l2, user_rtt_restore
- wrpr %g0, %g0, %otherwin
+661: wrpr %g0, %g0, %otherwin
+ .section .fast_win_ctrl_1insn_patch, "ax"
+ .word 661b
+ nop
+ .previous
ldx [%g6 + TI_FLAGS], %g3
wr %g0, ASI_AIUP, %asi
diff --git a/arch/sparc/kernel/setup_64.c b/arch/sparc/kernel/setup_64.c
index c4088a3..db4c4d7 100644
--- a/arch/sparc/kernel/setup_64.c
+++ b/arch/sparc/kernel/setup_64.c
@@ -300,6 +300,11 @@ static void __init sun4v_patch(void)
break;
}
+ if (sun4v_chip_type != SUN4V_CHIP_NIAGARA1) {
+ sun4v_patch_1insn_range(&__fast_win_ctrl_1insn_patch,
+ &__fast_win_ctrl_1insn_patch_end);
+ }
+
sun4v_hvapi_init();
}
diff --git a/arch/sparc/kernel/vmlinux.lds.S b/arch/sparc/kernel/vmlinux.lds.S
index 34d37e6..d78847d 100644
--- a/arch/sparc/kernel/vmlinux.lds.S
+++ b/arch/sparc/kernel/vmlinux.lds.S
@@ -159,6 +159,11 @@ SECTIONS
*(.pud_huge_patch)
__pud_huge_patch_end = .;
}
+ .fast_win_ctrl_1insn_patch : {
+ __fast_win_ctrl_1insn_patch = .;
+ *(.fast_win_ctrl_1insn_patch)
+ __fast_win_ctrl_1insn_patch_end = .;
+ }
PERCPU_SECTION(SMP_CACHE_BYTES)
#ifdef CONFIG_JUMP_LABEL
--
1.7.1
--
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