[v7,1/2] x86: Update large memcpy case in memmove-vec-unaligned-erms.S

Message ID 20210402213536.1380514-1-goldstein.w.n@gmail.com
State Superseded
Headers show
Series
  • [v7,1/2] x86: Update large memcpy case in memmove-vec-unaligned-erms.S
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Commit Message

Wei-Lun Chao via Libc-alpha April 2, 2021, 9:35 p.m.
From: noah <goldstein.w.n@gmail.com>


No Bug. This commit updates the large memcpy case (no overlap). The
update is to perform memcpy on either 2 or 4 contiguous pages at
once. This 1) helps to alleviate the affects of false memory aliasing
when destination and source have a close 4k alignment and 2) In most
cases and for most DRAM units is a modestly more efficient access
pattern. These changes are a clear performance improvement for
VEC_SIZE =16/32, though more ambiguous for VEC_SIZE=64. test-memcpy,
test-memccpy, test-mempcpy, test-memmove, and tst-memmove-overflow all
pass.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>

---
 .../multiarch/memmove-vec-unaligned-erms.S    | 307 ++++++++++++++----
 1 file changed, 245 insertions(+), 62 deletions(-)

-- 
2.29.2

Patch

diff --git a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
index 897a3d9762..9c7f95c653 100644
--- a/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
+++ b/sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
@@ -35,7 +35,16 @@ 
       __x86_rep_movsb_stop_threshold, then REP MOVSB will be used.
    7. If size >= __x86_shared_non_temporal_threshold and there is no
       overlap between destination and source, use non-temporal store
-      instead of aligned store.  */
+      instead of aligned store copying from either 2 or 4 pages at
+      once.
+   8. For point 7) if size < 16 * __x86_shared_non_temporal_threshold
+      and source and destination do not page alias, copy from 2 pages
+      at once using non-temporal stores. Page aliasing in this case is
+      considered true if destination's page alignment - sources' page
+      alignment is less than 8 * VEC_SIZE.
+   9. If size >= 16 * __x86_shared_non_temporal_threshold or source
+      and destination do page alias copy from 4 pages at once using
+      non-temporal stores.  */
 
 #include <sysdep.h>
 
@@ -67,6 +76,34 @@ 
 # endif
 #endif
 
+#ifndef PAGE_SIZE
+# define PAGE_SIZE 4096
+#endif
+
+#if PAGE_SIZE != 4096
+# error Unsupported PAGE_SIZE
+#endif
+
+#ifndef LOG_PAGE_SIZE
+# define LOG_PAGE_SIZE 12
+#endif
+
+#if PAGE_SIZE != (1 << LOG_PAGE_SIZE)
+# error Invalid LOG_PAGE_SIZE
+#endif
+
+/* Byte per page for large_memcpy inner loop.  */
+#if VEC_SIZE == 64
+# define LARGE_LOAD_SIZE (VEC_SIZE * 2)
+#else
+# define LARGE_LOAD_SIZE (VEC_SIZE * 4)
+#endif
+
+/* Amount to shift rdx by to compare for memcpy_large_4x.  */
+#ifndef LOG_4X_MEMCPY_THRESH
+# define LOG_4X_MEMCPY_THRESH 4
+#endif
+
 /* Avoid short distance rep movsb only with non-SSE vector.  */
 #ifndef AVOID_SHORT_DISTANCE_REP_MOVSB
 # define AVOID_SHORT_DISTANCE_REP_MOVSB (VEC_SIZE > 16)
@@ -106,6 +143,28 @@ 
 # error Unsupported PREFETCH_SIZE!
 #endif
 
+#if LARGE_LOAD_SIZE == (VEC_SIZE * 2)
+# define LOAD_ONE_SET(base, offset, vec0, vec1, ...) \
+	VMOVU	(offset)base, vec0; \
+	VMOVU	((offset) + VEC_SIZE)base, vec1;
+# define STORE_ONE_SET(base, offset, vec0, vec1, ...) \
+	VMOVNT  vec0, (offset)base; \
+	VMOVNT  vec1, ((offset) + VEC_SIZE)base;
+#elif LARGE_LOAD_SIZE == (VEC_SIZE * 4)
+# define LOAD_ONE_SET(base, offset, vec0, vec1, vec2, vec3) \
+	VMOVU	(offset)base, vec0; \
+	VMOVU	((offset) + VEC_SIZE)base, vec1; \
+	VMOVU	((offset) + VEC_SIZE * 2)base, vec2; \
+	VMOVU	((offset) + VEC_SIZE * 3)base, vec3;
+# define STORE_ONE_SET(base, offset, vec0, vec1, vec2, vec3) \
+	VMOVNT	vec0, (offset)base; \
+	VMOVNT	vec1, ((offset) + VEC_SIZE)base; \
+	VMOVNT	vec2, ((offset) + VEC_SIZE * 2)base; \
+	VMOVNT	vec3, ((offset) + VEC_SIZE * 3)base;
+#else
+# error Invalid LARGE_LOAD_SIZE
+#endif
+
 #ifndef SECTION
 # error SECTION is not defined!
 #endif
@@ -393,6 +452,15 @@  L(last_4x_vec):
 	VZEROUPPER_RETURN
 
 L(more_8x_vec):
+	/* Check if non-temporal move candidate.  */
+#if (defined USE_MULTIARCH || VEC_SIZE == 16) && IS_IN (libc)
+	/* Check non-temporal store threshold.  */
+	cmp __x86_shared_non_temporal_threshold(%rip), %RDX_LP
+	ja	L(large_memcpy_2x)
+#endif
+	/* Entry if rdx is greater than non-temporal threshold but there
+       is overlap.  */
+L(more_8x_vec_check):
 	cmpq	%rsi, %rdi
 	ja	L(more_8x_vec_backward)
 	/* Source == destination is less common.  */
@@ -419,11 +487,6 @@  L(more_8x_vec):
 	subq	%r8, %rdi
 	/* Adjust length.  */
 	addq	%r8, %rdx
-#if (defined USE_MULTIARCH || VEC_SIZE == 16) && IS_IN (libc)
-	/* Check non-temporal store threshold.  */
-	cmp	__x86_shared_non_temporal_threshold(%rip), %RDX_LP
-	ja	L(large_forward)
-#endif
 L(loop_4x_vec_forward):
 	/* Copy 4 * VEC a time forward.  */
 	VMOVU	(%rsi), %VEC(0)
@@ -470,11 +533,6 @@  L(more_8x_vec_backward):
 	subq	%r8, %r9
 	/* Adjust length.  */
 	subq	%r8, %rdx
-#if (defined USE_MULTIARCH || VEC_SIZE == 16) && IS_IN (libc)
-	/* Check non-temporal store threshold.  */
-	cmp	__x86_shared_non_temporal_threshold(%rip), %RDX_LP
-	ja	L(large_backward)
-#endif
 L(loop_4x_vec_backward):
 	/* Copy 4 * VEC a time backward.  */
 	VMOVU	(%rcx), %VEC(0)
@@ -500,72 +558,197 @@  L(loop_4x_vec_backward):
 	VZEROUPPER_RETURN
 
 #if (defined USE_MULTIARCH || VEC_SIZE == 16) && IS_IN (libc)
-L(large_forward):
+L(large_memcpy_2x):
+	/* Compute absolute value of difference between source and
+	   destination.  */
+	movq	%rdi, %r9
+	subq	%rsi, %r9
+	movq	%r9, %r8
+	leaq	-1(%r9), %rcx
+	sarq	$63, %r8
+	xorq	%r8, %r9
+	subq	%r8, %r9
 	/* Don't use non-temporal store if there is overlap between
-	   destination and source since destination may be in cache
-	   when source is loaded.  */
-	leaq    (%rdi, %rdx), %r10
-	cmpq    %r10, %rsi
-	jb	L(loop_4x_vec_forward)
-L(loop_large_forward):
+	   destination and source since destination may be in cache when
+	   source is loaded.  */
+	cmpq	%r9, %rdx
+	ja	L(more_8x_vec_check)
+
+	/* Cache align destination. First store the first 64 bytes then
+	   adjust alignments.  */
+	VMOVU	(%rsi), %VEC(8)
+#if VEC_SIZE < 64
+	VMOVU	VEC_SIZE(%rsi), %VEC(9)
+#if VEC_SIZE < 32
+	VMOVU	(VEC_SIZE * 2)(%rsi), %VEC(10)
+	VMOVU	(VEC_SIZE * 3)(%rsi), %VEC(11)
+#endif
+#endif
+	VMOVU	%VEC(8), (%rdi)
+#if VEC_SIZE < 64
+	VMOVU	%VEC(9), VEC_SIZE(%rdi)
+#if VEC_SIZE < 32
+	VMOVU	%VEC(10), (VEC_SIZE * 2)(%rdi)
+	VMOVU	%VEC(11), (VEC_SIZE * 3)(%rdi)
+#endif
+#endif
+	/* Adjust source, destination, and size.  */
+	movq	%rdi, %r8
+	andq	$63, %r8
+	/* Get the negative of offset for alignment.  */
+	subq	$64, %r8
+	/* Adjust source.  */
+	subq	%r8, %rsi
+	/* Adjust destination which should be aligned now.  */
+	subq	%r8, %rdi
+	/* Adjust length.  */
+	addq	%r8, %rdx
+
+	/* Test if source and destination addresses will alias. If they do
+	   the larger pipeline in large_memcpy_4x alleviated the
+	   performance drop.  */
+	testl	$(PAGE_SIZE - VEC_SIZE * 8), %ecx
+	jz	L(large_memcpy_4x)
+
+	movq	%rdx, %r10
+	shrq	$LOG_4X_MEMCPY_THRESH, %r10
+	cmp	__x86_shared_non_temporal_threshold(%rip), %r10
+	jae	L(large_memcpy_4x)
+
+	/* edx will store remainder size for copying tail.  */
+	andl	$(PAGE_SIZE * 2 - 1), %edx
+	/* r10 stores outer loop counter.  */
+	shrq	$((LOG_PAGE_SIZE + 1) - LOG_4X_MEMCPY_THRESH), %r10
+	/* Copy 4x VEC at a time from 2 pages.  */
+L(loop_large_memcpy_2x_outer):
+	/* ecx stores inner loop counter.  */
+	movl	$(PAGE_SIZE / LARGE_LOAD_SIZE), %ecx
+L(loop_large_memcpy_2x_inner):
+	PREFETCH_ONE_SET(1, (%rsi), PREFETCHED_LOAD_SIZE)
+	PREFETCH_ONE_SET(1, (%rsi), PREFETCHED_LOAD_SIZE * 2)
+	PREFETCH_ONE_SET(1, (%rsi), PAGE_SIZE + PREFETCHED_LOAD_SIZE)
+	PREFETCH_ONE_SET(1, (%rsi), PAGE_SIZE + PREFETCHED_LOAD_SIZE * 2)
+	/* Load vectors from rsi.  */
+	LOAD_ONE_SET((%rsi), 0, %VEC(0), %VEC(1), %VEC(2), %VEC(3))
+	LOAD_ONE_SET((%rsi), PAGE_SIZE, %VEC(4), %VEC(5), %VEC(6), %VEC(7))
+	addq	$LARGE_LOAD_SIZE, %rsi
+	/* Non-temporal store vectors to rdi.  */
+	STORE_ONE_SET((%rdi), 0, %VEC(0), %VEC(1), %VEC(2), %VEC(3))
+	STORE_ONE_SET((%rdi), PAGE_SIZE, %VEC(4), %VEC(5), %VEC(6), %VEC(7))
+	addq	$LARGE_LOAD_SIZE, %rdi
+	decl	%ecx
+	jnz	L(loop_large_memcpy_2x_inner)
+	addq	$PAGE_SIZE, %rdi
+	addq	$PAGE_SIZE, %rsi
+	decq	%r10
+	jne	L(loop_large_memcpy_2x_outer)
+
+	/* Check if only last 4 loads are needed.  */
+	cmpl	$(VEC_SIZE * 4), %edx
+	jbe	L(large_memcpy_2x_end)
+
+	/* Handle the last 2 * PAGE_SIZE bytes.  */
+L(loop_large_memcpy_2x_tail):
 	/* Copy 4 * VEC a time forward with non-temporal stores.  */
-	PREFETCH_ONE_SET (1, (%rsi), PREFETCHED_LOAD_SIZE * 2)
-	PREFETCH_ONE_SET (1, (%rsi), PREFETCHED_LOAD_SIZE * 3)
+	PREFETCH_ONE_SET (1, (%rsi), PREFETCHED_LOAD_SIZE)
 	VMOVU	(%rsi), %VEC(0)
 	VMOVU	VEC_SIZE(%rsi), %VEC(1)
 	VMOVU	(VEC_SIZE * 2)(%rsi), %VEC(2)
 	VMOVU	(VEC_SIZE * 3)(%rsi), %VEC(3)
-	addq	$PREFETCHED_LOAD_SIZE, %rsi
-	subq	$PREFETCHED_LOAD_SIZE, %rdx
+	addq	$(VEC_SIZE * 4), %rsi
+	subl	$(VEC_SIZE * 4), %edx
 	VMOVNT	%VEC(0), (%rdi)
 	VMOVNT	%VEC(1), VEC_SIZE(%rdi)
 	VMOVNT	%VEC(2), (VEC_SIZE * 2)(%rdi)
 	VMOVNT	%VEC(3), (VEC_SIZE * 3)(%rdi)
-	addq	$PREFETCHED_LOAD_SIZE, %rdi
-	cmpq	$PREFETCHED_LOAD_SIZE, %rdx
-	ja	L(loop_large_forward)
+	addq	$(VEC_SIZE * 4), %rdi
+	cmpl	$(VEC_SIZE * 4), %edx
+	ja	L(loop_large_memcpy_2x_tail)
+
+L(large_memcpy_2x_end):
 	sfence
 	/* Store the last 4 * VEC.  */
-	VMOVU	%VEC(5), (%rcx)
-	VMOVU	%VEC(6), -VEC_SIZE(%rcx)
-	VMOVU	%VEC(7), -(VEC_SIZE * 2)(%rcx)
-	VMOVU	%VEC(8), -(VEC_SIZE * 3)(%rcx)
-	/* Store the first VEC.  */
-	VMOVU	%VEC(4), (%r11)
+	VMOVU	-(VEC_SIZE * 4)(%rsi, %rdx), %VEC(0)
+	VMOVU	-(VEC_SIZE * 3)(%rsi, %rdx), %VEC(1)
+	VMOVU	-(VEC_SIZE * 2)(%rsi, %rdx), %VEC(2)
+	VMOVU	-VEC_SIZE(%rsi, %rdx), %VEC(3)
+
+	VMOVU	%VEC(0), -(VEC_SIZE * 4)(%rdi, %rdx)
+	VMOVU	%VEC(1), -(VEC_SIZE * 3)(%rdi, %rdx)
+	VMOVU	%VEC(2), -(VEC_SIZE * 2)(%rdi, %rdx)
+	VMOVU	%VEC(3), -VEC_SIZE(%rdi, %rdx)
 	VZEROUPPER_RETURN
 
-L(large_backward):
-	/* Don't use non-temporal store if there is overlap between
-	   destination and source since destination may be in cache
-	   when source is loaded.  */
-	leaq    (%rcx, %rdx), %r10
-	cmpq    %r10, %r9
-	jb	L(loop_4x_vec_backward)
-L(loop_large_backward):
-	/* Copy 4 * VEC a time backward with non-temporal stores.  */
-	PREFETCH_ONE_SET (-1, (%rcx), -PREFETCHED_LOAD_SIZE * 2)
-	PREFETCH_ONE_SET (-1, (%rcx), -PREFETCHED_LOAD_SIZE * 3)
-	VMOVU	(%rcx), %VEC(0)
-	VMOVU	-VEC_SIZE(%rcx), %VEC(1)
-	VMOVU	-(VEC_SIZE * 2)(%rcx), %VEC(2)
-	VMOVU	-(VEC_SIZE * 3)(%rcx), %VEC(3)
-	subq	$PREFETCHED_LOAD_SIZE, %rcx
-	subq	$PREFETCHED_LOAD_SIZE, %rdx
-	VMOVNT	%VEC(0), (%r9)
-	VMOVNT	%VEC(1), -VEC_SIZE(%r9)
-	VMOVNT	%VEC(2), -(VEC_SIZE * 2)(%r9)
-	VMOVNT	%VEC(3), -(VEC_SIZE * 3)(%r9)
-	subq	$PREFETCHED_LOAD_SIZE, %r9
-	cmpq	$PREFETCHED_LOAD_SIZE, %rdx
-	ja	L(loop_large_backward)
+L(large_memcpy_4x):
+	movq	%rdx, %r10
+	/* edx will store remainder size for copying tail.  */
+	andl	$(PAGE_SIZE * 4 - 1), %edx
+	/* r10 stores outer loop counter.  */
+	shrq	$(LOG_PAGE_SIZE + 2), %r10
+	/* Copy 4x VEC at a time from 4 pages.  */
+L(loop_large_memcpy_4x_outer):
+	/* ecx stores inner loop counter.  */
+	movl	$(PAGE_SIZE / LARGE_LOAD_SIZE), %ecx
+L(loop_large_memcpy_4x_inner):
+	/* Only one prefetch set per page as doing 4 pages give more time
+	   for prefetcher to keep up.  */
+	PREFETCH_ONE_SET(1, (%rsi), PREFETCHED_LOAD_SIZE)
+	PREFETCH_ONE_SET(1, (%rsi), PAGE_SIZE + PREFETCHED_LOAD_SIZE)
+	PREFETCH_ONE_SET(1, (%rsi), PAGE_SIZE * 2 + PREFETCHED_LOAD_SIZE)
+	PREFETCH_ONE_SET(1, (%rsi), PAGE_SIZE * 3 + PREFETCHED_LOAD_SIZE)
+	/* Load vectors from rsi.  */
+	LOAD_ONE_SET((%rsi), 0, %VEC(0), %VEC(1), %VEC(2), %VEC(3))
+	LOAD_ONE_SET((%rsi), PAGE_SIZE, %VEC(4), %VEC(5), %VEC(6), %VEC(7))
+	LOAD_ONE_SET((%rsi), PAGE_SIZE * 2, %VEC(8), %VEC(9), %VEC(10), %VEC(11))
+	LOAD_ONE_SET((%rsi), PAGE_SIZE * 3, %VEC(12), %VEC(13), %VEC(14), %VEC(15))
+	addq	$LARGE_LOAD_SIZE, %rsi
+	/* Non-temporal store vectors to rdi.  */
+	STORE_ONE_SET((%rdi), 0, %VEC(0), %VEC(1), %VEC(2), %VEC(3))
+	STORE_ONE_SET((%rdi), PAGE_SIZE, %VEC(4), %VEC(5), %VEC(6), %VEC(7))
+	STORE_ONE_SET((%rdi), PAGE_SIZE * 2, %VEC(8), %VEC(9), %VEC(10), %VEC(11))
+	STORE_ONE_SET((%rdi), PAGE_SIZE * 3, %VEC(12), %VEC(13), %VEC(14), %VEC(15))
+	addq	$LARGE_LOAD_SIZE, %rdi
+	decl	%ecx
+	jnz	L(loop_large_memcpy_4x_inner)
+	addq	$(PAGE_SIZE * 3), %rdi
+	addq	$(PAGE_SIZE * 3), %rsi
+	decq	%r10
+	jne	L(loop_large_memcpy_4x_outer)
+
+	/* Check if only last 4 loads are needed.  */
+	cmpl	$(VEC_SIZE * 4), %edx
+	jbe	L(large_memcpy_4x_end)
+
+	/* Handle the last 4  * PAGE_SIZE bytes.  */
+L(loop_large_memcpy_4x_tail):
+	/* Copy 4 * VEC a time forward with non-temporal stores.  */
+	PREFETCH_ONE_SET (1, (%rsi), PREFETCHED_LOAD_SIZE)
+	VMOVU	(%rsi), %VEC(0)
+	VMOVU	VEC_SIZE(%rsi), %VEC(1)
+	VMOVU	(VEC_SIZE * 2)(%rsi), %VEC(2)
+	VMOVU	(VEC_SIZE * 3)(%rsi), %VEC(3)
+	addq	$(VEC_SIZE * 4), %rsi
+	subl	$(VEC_SIZE * 4), %edx
+	VMOVNT	%VEC(0), (%rdi)
+	VMOVNT	%VEC(1), VEC_SIZE(%rdi)
+	VMOVNT	%VEC(2), (VEC_SIZE * 2)(%rdi)
+	VMOVNT	%VEC(3), (VEC_SIZE * 3)(%rdi)
+	addq	$(VEC_SIZE * 4), %rdi
+	cmpl	$(VEC_SIZE * 4), %edx
+	ja	L(loop_large_memcpy_4x_tail)
+
+L(large_memcpy_4x_end):
 	sfence
-	/* Store the first 4 * VEC.  */
-	VMOVU	%VEC(4), (%rdi)
-	VMOVU	%VEC(5), VEC_SIZE(%rdi)
-	VMOVU	%VEC(6), (VEC_SIZE * 2)(%rdi)
-	VMOVU	%VEC(7), (VEC_SIZE * 3)(%rdi)
-	/* Store the last VEC.  */
-	VMOVU	%VEC(8), (%r11)
+	/* Store the last 4 * VEC.  */
+	VMOVU	-(VEC_SIZE * 4)(%rsi, %rdx), %VEC(0)
+	VMOVU	-(VEC_SIZE * 3)(%rsi, %rdx), %VEC(1)
+	VMOVU	-(VEC_SIZE * 2)(%rsi, %rdx), %VEC(2)
+	VMOVU	-VEC_SIZE(%rsi, %rdx), %VEC(3)
+
+	VMOVU	%VEC(0), -(VEC_SIZE * 4)(%rdi, %rdx)
+	VMOVU	%VEC(1), -(VEC_SIZE * 3)(%rdi, %rdx)
+	VMOVU	%VEC(2), -(VEC_SIZE * 2)(%rdi, %rdx)
+	VMOVU	%VEC(3), -VEC_SIZE(%rdi, %rdx)
 	VZEROUPPER_RETURN
 #endif
 END (MEMMOVE_SYMBOL (__memmove, unaligned_erms))