[PATCH v5 2/4] powerpc/64: enhance memcmp() with VMX instruction for long bytes comparision
From: <hidden>
Date: 2018-05-23 07:33:09
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
From: Simon Guo <redacted> This patch add VMX primitives to do memcmp() in case the compare size exceeds 4K bytes. KSM feature can benefit from this. Test result with following test program(replace the "^>" with ""): ------
# cat tools/testing/selftests/powerpc/stringloops/memcmp.c #include <malloc.h> #include <stdlib.h> #include <string.h> #include <time.h> #include "utils.h" #define SIZE (1024 * 1024 * 900) #define ITERATIONS 40
int test_memcmp(const void *s1, const void *s2, size_t n);
static int testcase(void)
{
char *s1;
char *s2;
unsigned long i;
s1 = memalign(128, SIZE);
if (!s1) {
perror("memalign");
exit(1);
}
s2 = memalign(128, SIZE);
if (!s2) {
perror("memalign");
exit(1);
}
for (i = 0; i < SIZE; i++) {
s1[i] = i & 0xff;
s2[i] = i & 0xff;
}
for (i = 0; i < ITERATIONS; i++) {
int ret = test_memcmp(s1, s2, SIZE);
if (ret) {
printf("return %d at[%ld]! should have returned zero\n", ret, i);
abort();
}
}
return 0;
}
int main(void)
{
return test_harness(testcase, "memcmp");
}
------
Without this patch (but with the first patch "powerpc/64: Align bytes
before fall back to .Lshort in powerpc64 memcmp()." in the series):
4.726728762 seconds time elapsed ( +- 3.54%)
With VMX patch:
4.234335473 seconds time elapsed ( +- 2.63%)
There is ~+10% improvement.
Testing with unaligned and different offset version (make s1 and s2 shift
random offset within 16 bytes) can archieve higher improvement than 10%..
Signed-off-by: Simon Guo <redacted>
---
arch/powerpc/include/asm/asm-prototypes.h | 4 +-
arch/powerpc/lib/copypage_power7.S | 4 +-
arch/powerpc/lib/memcmp_64.S | 231 ++++++++++++++++++++++++++++++
arch/powerpc/lib/memcpy_power7.S | 6 +-
arch/powerpc/lib/vmx-helper.c | 4 +-
5 files changed, 240 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/include/asm/asm-prototypes.h b/arch/powerpc/include/asm/asm-prototypes.h
index d9713ad..31fdcee 100644
--- a/arch/powerpc/include/asm/asm-prototypes.h
+++ b/arch/powerpc/include/asm/asm-prototypes.h@@ -49,8 +49,8 @@ void __trace_hcall_exit(long opcode, unsigned long retval, /* VMX copying */ int enter_vmx_usercopy(void); int exit_vmx_usercopy(void); -int enter_vmx_copy(void); -void * exit_vmx_copy(void *dest); +int enter_vmx_ops(void); +void *exit_vmx_ops(void *dest); /* Traps */ long machine_check_early(struct pt_regs *regs);
diff --git a/arch/powerpc/lib/copypage_power7.S b/arch/powerpc/lib/copypage_power7.S
index 8fa73b7..e38f956 100644
--- a/arch/powerpc/lib/copypage_power7.S
+++ b/arch/powerpc/lib/copypage_power7.S@@ -57,7 +57,7 @@ _GLOBAL(copypage_power7) std r4,-STACKFRAMESIZE+STK_REG(R30)(r1) std r0,16(r1) stdu r1,-STACKFRAMESIZE(r1) - bl enter_vmx_copy + bl enter_vmx_ops cmpwi r3,0 ld r0,STACKFRAMESIZE+16(r1) ld r3,STK_REG(R31)(r1)
@@ -100,7 +100,7 @@ _GLOBAL(copypage_power7) addi r3,r3,128 bdnz 1b - b exit_vmx_copy /* tail call optimise */ + b exit_vmx_ops /* tail call optimise */ #else li r0,(PAGE_SIZE/128)
diff --git a/arch/powerpc/lib/memcmp_64.S b/arch/powerpc/lib/memcmp_64.S
index f20e883..6303bbf 100644
--- a/arch/powerpc/lib/memcmp_64.S
+++ b/arch/powerpc/lib/memcmp_64.S@@ -27,12 +27,73 @@ #define LH lhbrx #define LW lwbrx #define LD ldbrx +#define LVS lvsr +#define VPERM(_VRT,_VRA,_VRB,_VRC) \ + vperm _VRT,_VRB,_VRA,_VRC #else #define LH lhzx #define LW lwzx #define LD ldx +#define LVS lvsl +#define VPERM(_VRT,_VRA,_VRB,_VRC) \ + vperm _VRT,_VRA,_VRB,_VRC #endif +#define VMX_OPS_THRES 4096 +#define ENTER_VMX_OPS \ + mflr r0; \ + std r3,-STACKFRAMESIZE+STK_REG(R31)(r1); \ + std r4,-STACKFRAMESIZE+STK_REG(R30)(r1); \ + std r5,-STACKFRAMESIZE+STK_REG(R29)(r1); \ + std r0,16(r1); \ + stdu r1,-STACKFRAMESIZE(r1); \ + bl enter_vmx_ops; \ + cmpwi cr1,r3,0; \ + ld r0,STACKFRAMESIZE+16(r1); \ + ld r3,STK_REG(R31)(r1); \ + ld r4,STK_REG(R30)(r1); \ + ld r5,STK_REG(R29)(r1); \ + addi r1,r1,STACKFRAMESIZE; \ + mtlr r0 + +#define EXIT_VMX_OPS \ + mflr r0; \ + std r3,-STACKFRAMESIZE+STK_REG(R31)(r1); \ + std r4,-STACKFRAMESIZE+STK_REG(R30)(r1); \ + std r5,-STACKFRAMESIZE+STK_REG(R29)(r1); \ + std r0,16(r1); \ + stdu r1,-STACKFRAMESIZE(r1); \ + bl exit_vmx_ops; \ + ld r0,STACKFRAMESIZE+16(r1); \ + ld r3,STK_REG(R31)(r1); \ + ld r4,STK_REG(R30)(r1); \ + ld r5,STK_REG(R29)(r1); \ + addi r1,r1,STACKFRAMESIZE; \ + mtlr r0 + +/* + * LD_VSR_CROSS16B load the 2nd 16 bytes for _vaddr which is unaligned with + * 16 bytes boundary and permute the result with the 1st 16 bytes. + + * | y y y y y y y y y y y y y 0 1 2 | 3 4 5 6 7 8 9 a b c d e f z z z | + * ^ ^ ^ + * 0xbbbb10 0xbbbb20 0xbbb30 + * ^ + * _vaddr + * + * + * _vmask is the mask generated by LVS + * _v1st_qw is the 1st aligned QW of current addr which is already loaded. + * for example: 0xyyyyyyyyyyyyy012 for big endian + * _v2nd_qw is the 2nd aligned QW of cur _vaddr to be loaded. + * for example: 0x3456789abcdefzzz for big endian + * The permute result is saved in _v_res. + * for example: 0x0123456789abcdef for big endian. + */ +#define LD_VSR_CROSS16B(_vaddr,_vmask,_v1st_qw,_v2nd_qw,_v_res) \ + lvx _v2nd_qw,_vaddr,off16; \ + VPERM(_v_res,_v1st_qw,_v2nd_qw,_vmask) + /* * There are 2 categories for memcmp: * 1) src/dst has the same offset to the 8 bytes boundary. The handlers
@@ -174,6 +235,13 @@ _GLOBAL(memcmp) blr .Llong: +#ifdef CONFIG_ALTIVEC + /* Try to use vmx loop if length is larger than 4K */ + cmpldi cr6,r5,VMX_OPS_THRES + bge cr6,.Lsameoffset_vmx_cmp + +.Llong_novmx_cmp: +#endif /* At least s1 addr is aligned with 8 bytes */ li off8,8 li off16,16
@@ -332,7 +400,94 @@ _GLOBAL(memcmp) 8: blr +#ifdef CONFIG_ALTIVEC +.Lsameoffset_vmx_cmp: + /* Enter with src/dst addrs has the same offset with 8 bytes + * align boundary + */ + ENTER_VMX_OPS + beq cr1,.Llong_novmx_cmp + +3: + /* need to check whether r4 has the same offset with r3 + * for 16 bytes boundary. + */ + xor r0,r3,r4 + andi. r0,r0,0xf + bne .Ldiffoffset_vmx_cmp_start + + /* len is no less than 4KB. Need to align with 16 bytes further. + */ + andi. rA,r3,8 + LD rA,0,r3 + beq 4f + LD rB,0,r4 + cmpld cr0,rA,rB + addi r3,r3,8 + addi r4,r4,8 + addi r5,r5,-8 + + beq cr0,4f + /* save and restore cr0 */ + mfocrf r5,64 + EXIT_VMX_OPS + mtocrf 64,r5 + b .LcmpAB_lightweight + +4: + /* compare 32 bytes for each loop */ + srdi r0,r5,5 + mtctr r0 + clrldi r5,r5,59 + li off16,16 + +.balign 16 +5: + lvx v0,0,r3 + lvx v1,0,r4 + vcmpequd. v0,v0,v1 + bf 24,7f + lvx v0,off16,r3 + lvx v1,off16,r4 + vcmpequd. v0,v0,v1 + bf 24,6f + addi r3,r3,32 + addi r4,r4,32 + bdnz 5b + + EXIT_VMX_OPS + cmpdi r5,0 + beq .Lzero + b .Lcmp_lt32bytes + +6: + addi r3,r3,16 + addi r4,r4,16 + +7: + /* diff the last 16 bytes */ + EXIT_VMX_OPS + LD rA,0,r3 + LD rB,0,r4 + cmpld cr0,rA,rB + li off8,8 + bne cr0,.LcmpAB_lightweight + + LD rA,off8,r3 + LD rB,off8,r4 + cmpld cr0,rA,rB + bne cr0,.LcmpAB_lightweight + b .Lzero +#endif + .Ldiffoffset_8bytes_make_align_start: +#ifdef CONFIG_ALTIVEC + /* only do vmx ops when the size exceeds 4K bytes */ + cmpdi cr5,r5,VMX_OPS_THRES + bge cr5,.Ldiffoffset_vmx_cmp +.Ldiffoffset_novmx_cmp: +#endif + /* now try to align s1 with 8 bytes */ andi. r6,r3,0x7 rlwinm r6,r6,3,0,28
@@ -359,6 +514,82 @@ _GLOBAL(memcmp) /* now s1 is aligned with 8 bytes. */ cmpdi cr5,r5,31 ble cr5,.Lcmp_lt32bytes + +#ifdef CONFIG_ALTIVEC + b .Llong_novmx_cmp +#else b .Llong +#endif + +#ifdef CONFIG_ALTIVEC +.Ldiffoffset_vmx_cmp: + ENTER_VMX_OPS + beq cr1,.Ldiffoffset_novmx_cmp + +.Ldiffoffset_vmx_cmp_start: + /* Firstly try to align r3 with 16 bytes */ + andi. r6,r3,0xf + li off16,16 + beq .Ldiffoffset_vmx_s1_16bytes_align + LVS v3,0,r3 + LVS v4,0,r4 + + lvx v5,0,r3 + lvx v6,0,r4 + LD_VSR_CROSS16B(r3,v3,v5,v7,v9) + LD_VSR_CROSS16B(r4,v4,v6,v8,v10) + + vcmpequb. v7,v9,v10 + bnl cr6,.Ldiffoffset_vmx_diff_found + + subfic r6,r6,16 + subf r5,r6,r5 + add r3,r3,r6 + add r4,r4,r6 + +.Ldiffoffset_vmx_s1_16bytes_align: + /* now s1 is aligned with 16 bytes */ + lvx v6,0,r4 + LVS v4,0,r4 + srdi r6,r5,5 /* loop for 32 bytes each */ + clrldi r5,r5,59 + mtctr r6 + +.balign 16 +.Ldiffoffset_vmx_32bytesloop: + /* the first qw of r4 was saved in v6 */ + lvx v9,0,r3 + LD_VSR_CROSS16B(r4,v4,v6,v8,v10) + vcmpequb. v7,v9,v10 + vor v6,v8,v8 + bnl cr6,.Ldiffoffset_vmx_diff_found + + addi r3,r3,16 + addi r4,r4,16 + + lvx v9,0,r3 + LD_VSR_CROSS16B(r4,v4,v6,v8,v10) + vcmpequb. v7,v9,v10 + vor v6,v8,v8 + bnl cr6,.Ldiffoffset_vmx_diff_found + + addi r3,r3,16 + addi r4,r4,16 + + bdnz .Ldiffoffset_vmx_32bytesloop + + EXIT_VMX_OPS + + cmpdi r5,0 + beq .Lzero + b .Lcmp_lt32bytes + +.Ldiffoffset_vmx_diff_found: + EXIT_VMX_OPS + /* anyway, the diff will appear in next 16 bytes */ + li r5,16 + b .Lcmp_lt32bytes + +#endif EXPORT_SYMBOL(memcmp)
diff --git a/arch/powerpc/lib/memcpy_power7.S b/arch/powerpc/lib/memcpy_power7.S
index df7de9d..070cdf6 100644
--- a/arch/powerpc/lib/memcpy_power7.S
+++ b/arch/powerpc/lib/memcpy_power7.S@@ -230,7 +230,7 @@ _GLOBAL(memcpy_power7) std r5,-STACKFRAMESIZE+STK_REG(R29)(r1) std r0,16(r1) stdu r1,-STACKFRAMESIZE(r1) - bl enter_vmx_copy + bl enter_vmx_ops cmpwi cr1,r3,0 ld r0,STACKFRAMESIZE+16(r1) ld r3,STK_REG(R31)(r1)
@@ -445,7 +445,7 @@ _GLOBAL(memcpy_power7) 15: addi r1,r1,STACKFRAMESIZE ld r3,-STACKFRAMESIZE+STK_REG(R31)(r1) - b exit_vmx_copy /* tail call optimise */ + b exit_vmx_ops /* tail call optimise */ .Lvmx_unaligned_copy: /* Get the destination 16B aligned */
@@ -649,5 +649,5 @@ _GLOBAL(memcpy_power7) 15: addi r1,r1,STACKFRAMESIZE ld r3,-STACKFRAMESIZE+STK_REG(R31)(r1) - b exit_vmx_copy /* tail call optimise */ + b exit_vmx_ops /* tail call optimise */ #endif /* CONFIG_ALTIVEC */
diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c
index bf925cd..9f34049 100644
--- a/arch/powerpc/lib/vmx-helper.c
+++ b/arch/powerpc/lib/vmx-helper.c@@ -53,7 +53,7 @@ int exit_vmx_usercopy(void) return 0; } -int enter_vmx_copy(void) +int enter_vmx_ops(void) { if (in_interrupt()) return 0;
@@ -70,7 +70,7 @@ int enter_vmx_copy(void) * passed a pointer to the destination which we return as required by a * memcpy implementation. */ -void *exit_vmx_copy(void *dest) +void *exit_vmx_ops(void *dest) { disable_kernel_altivec(); preempt_enable();
--
1.8.3.1