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sparc64: speed up etrap/rtrap on NG2 and later processors

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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>
This commit is contained in:
Anthony Yznaga 2017-08-18 12:40:36 -07:00 committed by David S. Miller
parent 5bd0ea9107
commit a7159a87a3
5 changed files with 45 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/sparc/include/asm/trap_block.h
View File

@ -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;

26
arch/sparc/kernel/etrap_64.S
View File

@ -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

13
arch/sparc/kernel/rtrap_64.S
View File

@ -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

5
arch/sparc/kernel/setup_64.c
View File

@ -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();
}

5
arch/sparc/kernel/vmlinux.lds.S
View File

@ -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