[PATCH 2/2] powerpc32: rewrite of csum_partial_copy_generic based of copy_tofrom_user

From: Christophe Leroy
Date: Mon Jun 22 2015 - 13:01:50 EST

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csum_partial_copy_generic() does the same as copy_tofrom_user and also
calculates the checksum during the copy. Unlike copy_tofrom_user(), the existing
version of csum_partial_copy_generic() doesn't take benefit of the cache

This patch is a rewrite of csum_partial_copy_generic() based on
copy_tofrom_user().
The previous version of csum_partial_copy_generic() was handling errors. Now we
have the checksum wrapper functions to handle the error case like in powerpc64
so we can make the error case simple: just return -EFAULT.
copy_tofrom_user() only has r12 available => we use it for the checksum
r7 and r8 which contains pointers to error feedback are used, so we stack them.

On a TCP benchmark using socklib on the loopback interface on which checksum
offload and scatter/gather have been deactivated, we get about 20% performance
increase.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
arch/powerpc/lib/checksum_32.S | 320 +++++++++++++++++++++++++++--------------
1 file changed, 209 insertions(+), 111 deletions(-)

diff --git a/arch/powerpc/lib/checksum_32.S b/arch/powerpc/lib/checksum_32.S
index 7874e8a..7b95a68 100644
--- a/arch/powerpc/lib/checksum_32.S
+++ b/arch/powerpc/lib/checksum_32.S
@@ -14,6 +14,7 @@

#include <linux/sys.h>
#include <asm/processor.h>
+#include <asm/cache.h>
#include <asm/errno.h>
#include <asm/ppc_asm.h>

@@ -103,123 +104,220 @@ _GLOBAL(csum_partial)
*
* csum_partial_copy_generic(src, dst, len, sum, src_err, dst_err)
*/
+#define CSUM_COPY_16_BYTES_WITHEX(n) \
+8 ## n ## 0: \
+ lwz r7,4(r4); \
+8 ## n ## 1: \
+ lwz r8,8(r4); \
+8 ## n ## 2: \
+ lwz r9,12(r4); \
+8 ## n ## 3: \
+ lwzu r10,16(r4); \
+8 ## n ## 4: \
+ stw r7,4(r6); \
+ adde r12,r12,r7; \
+8 ## n ## 5: \
+ stw r8,8(r6); \
+ adde r12,r12,r8; \
+8 ## n ## 6: \
+ stw r9,12(r6); \
+ adde r12,r12,r9; \
+8 ## n ## 7: \
+ stwu r10,16(r6); \
+ adde r12,r12,r10
+
+#define CSUM_COPY_16_BYTES_EXCODE(n) \
+.section __ex_table,"a"; \
+ .align 2; \
+ .long 8 ## n ## 0b,src_error; \
+ .long 8 ## n ## 1b,src_error; \
+ .long 8 ## n ## 2b,src_error; \
+ .long 8 ## n ## 3b,src_error; \
+ .long 8 ## n ## 4b,dst_error; \
+ .long 8 ## n ## 5b,dst_error; \
+ .long 8 ## n ## 6b,dst_error; \
+ .long 8 ## n ## 7b,dst_error; \
+ .text
+
+ .text
+ .stabs "arch/powerpc/lib/",N_SO,0,0,0f
+ .stabs "checksum_32.S",N_SO,0,0,0f
+0:
+
+CACHELINE_BYTES = L1_CACHE_BYTES
+LG_CACHELINE_BYTES = L1_CACHE_SHIFT
+CACHELINE_MASK = (L1_CACHE_BYTES-1)
+
_GLOBAL(csum_partial_copy_generic)
- addic r0,r6,0
- subi r3,r3,4
- subi r4,r4,4
- srwi. r6,r5,2
- beq 3f /* if we're doing < 4 bytes */
- andi. r9,r4,2 /* Align dst to longword boundary */
- beq+ 1f
-81: lhz r6,4(r3) /* do 2 bytes to get aligned */
- addi r3,r3,2
- subi r5,r5,2
-91: sth r6,4(r4)
- addi r4,r4,2
- addc r0,r0,r6
- srwi. r6,r5,2 /* # words to do */
- beq 3f
-1: srwi. r6,r5,4 /* # groups of 4 words to do */
- beq 10f
- mtctr r6
-71: lwz r6,4(r3)
-72: lwz r9,8(r3)
-73: lwz r10,12(r3)
-74: lwzu r11,16(r3)
- adde r0,r0,r6
-75: stw r6,4(r4)
- adde r0,r0,r9
-76: stw r9,8(r4)
- adde r0,r0,r10
-77: stw r10,12(r4)
- adde r0,r0,r11
-78: stwu r11,16(r4)
- bdnz 71b
-10: rlwinm. r6,r5,30,30,31 /* # words left to do */
- beq 13f
- mtctr r6
-82: lwzu r9,4(r3)
-92: stwu r9,4(r4)
- adde r0,r0,r9
- bdnz 82b
-13: andi. r5,r5,3
-3: cmpwi 0,r5,2
- blt+ 4f
-83: lhz r6,4(r3)
- addi r3,r3,2
- subi r5,r5,2
-93: sth r6,4(r4)
+ stwu r1,-16(r1)
+ stw r7,12(r1)
+ stw r8,8(r1)
+
+ andi. r0,r4,1 /* is destination address even ? */
+ cmplwi cr7,r0,0
+ addic r12,r6,0
+ addi r6,r4,-4
+ neg r0,r4
+ addi r4,r3,-4
+ andi. r0,r0,CACHELINE_MASK /* # bytes to start of cache line */
+ beq 58f
+
+ cmplw 0,r5,r0 /* is this more than total to do? */
+ blt 63f /* if not much to do */
+ andi. r8,r0,3 /* get it word-aligned first */
+ mtctr r8
+ beq+ 61f
+ li r3,0
+70: lbz r9,4(r4) /* do some bytes */
+ addi r4,r4,1
+ slwi r3,r3,8
+ rlwimi r3,r9,0,24,31
+71: stb r9,4(r6)
+ addi r6,r6,1
+ bdnz 70b
+ adde r12,r12,r3
+61: subf r5,r0,r5
+ srwi. r0,r0,2
+ mtctr r0
+ beq 58f
+72: lwzu r9,4(r4) /* do some words */
+ adde r12,r12,r9
+73: stwu r9,4(r6)
+ bdnz 72b
+
+58: srwi. r0,r5,LG_CACHELINE_BYTES /* # complete cachelines */
+ clrlwi r5,r5,32-LG_CACHELINE_BYTES
+ li r11,4
+ beq 63f
+
+ /* Here we decide how far ahead to prefetch the source */
+ li r3,4
+ cmpwi r0,1
+ li r7,0
+ ble 114f
+ li r7,1
+#if MAX_COPY_PREFETCH > 1
+ /* Heuristically, for large transfers we prefetch
+ MAX_COPY_PREFETCH cachelines ahead. For small transfers
+ we prefetch 1 cacheline ahead. */
+ cmpwi r0,MAX_COPY_PREFETCH
+ ble 112f
+ li r7,MAX_COPY_PREFETCH
+112: mtctr r7
+111: dcbt r3,r4
+ addi r3,r3,CACHELINE_BYTES
+ bdnz 111b
+#else
+ dcbt r3,r4
+ addi r3,r3,CACHELINE_BYTES
+#endif /* MAX_COPY_PREFETCH > 1 */
+
+114: subf r8,r7,r0
+ mr r0,r7
+ mtctr r8
+
+53: dcbt r3,r4
+54: dcbz r11,r6
+/* the main body of the cacheline loop */
+ CSUM_COPY_16_BYTES_WITHEX(0)
+#if L1_CACHE_BYTES >= 32
+ CSUM_COPY_16_BYTES_WITHEX(1)
+#if L1_CACHE_BYTES >= 64
+ CSUM_COPY_16_BYTES_WITHEX(2)
+ CSUM_COPY_16_BYTES_WITHEX(3)
+#if L1_CACHE_BYTES >= 128
+ CSUM_COPY_16_BYTES_WITHEX(4)
+ CSUM_COPY_16_BYTES_WITHEX(5)
+ CSUM_COPY_16_BYTES_WITHEX(6)
+ CSUM_COPY_16_BYTES_WITHEX(7)
+#endif
+#endif
+#endif
+ bdnz 53b
+ cmpwi r0,0
+ li r3,4
+ li r7,0
+ bne 114b
+
+63: srwi. r0,r5,2
+ mtctr r0
+ beq 64f
+30: lwzu r0,4(r4)
+ adde r12,r12,r0
+31: stwu r0,4(r6)
+ bdnz 30b
+
+64: andi. r0,r5,2
+ beq+ 65f
+40: lhz r0,4(r4)
addi r4,r4,2
- adde r0,r0,r6
-4: cmpwi 0,r5,1
- bne+ 5f
-84: lbz r6,4(r3)
-94: stb r6,4(r4)
- slwi r6,r6,8 /* Upper byte of word */
- adde r0,r0,r6
-5: addze r3,r0 /* add in final carry */
+41: sth r0,4(r6)
+ adde r12,r12,r0
+ addi r6,r6,2
+65: andi. r0,r5,1
+ beq+ 66f
+50: lbz r0,4(r4)
+51: stb r0,4(r6)
+ slwi r0,r0,8
+ adde r12,r12,r0
+66: addze r3,r12
+ addi r1,r1,16
+ beqlr+ cr7
+ rlwinm r3,r3,8,0,31 /* swap bytes for odd destination */
blr

-/* These shouldn't go in the fixup section, since that would
- cause the ex_table addresses to get out of order. */
-
-src_error_4:
- mfctr r6 /* update # bytes remaining from ctr */
- rlwimi r5,r6,4,0,27
- b 79f
-src_error_1:
- li r6,0
- subi r5,r5,2
-95: sth r6,4(r4)
- addi r4,r4,2
-79: srwi. r6,r5,2
- beq 3f
- mtctr r6
-src_error_2:
- li r6,0
-96: stwu r6,4(r4)
- bdnz 96b
-3: andi. r5,r5,3
- beq src_error
-src_error_3:
- li r6,0
- mtctr r5
- addi r4,r4,3
-97: stbu r6,1(r4)
- bdnz 97b
+/* read fault */
src_error:
- cmpwi 0,r7,0
- beq 1f
- li r6,-EFAULT
- stw r6,0(r7)
-1: addze r3,r0
+ lwz r7,12(r1)
+ addi r1,r1,16
+ cmpwi cr0,r7,0
+ beqlr
+ li r0,-EFAULT
+ stw r0,0(r7)
blr
-
+/* write fault */
dst_error:
- cmpwi 0,r8,0
- beq 1f
- li r6,-EFAULT
- stw r6,0(r8)
-1: addze r3,r0
+ lwz r8,8(r1)
+ addi r1,r1,16
+ cmpwi cr0,r8,0
+ beqlr
+ li r0,-EFAULT
+ stw r0,0(r8)
blr

-.section __ex_table,"a"
- .long 81b,src_error_1
- .long 91b,dst_error
- .long 71b,src_error_4
- .long 72b,src_error_4
- .long 73b,src_error_4
- .long 74b,src_error_4
- .long 75b,dst_error
- .long 76b,dst_error
- .long 77b,dst_error
- .long 78b,dst_error
- .long 82b,src_error_2
- .long 92b,dst_error
- .long 83b,src_error_3
- .long 93b,dst_error
- .long 84b,src_error_3
- .long 94b,dst_error
- .long 95b,dst_error
- .long 96b,dst_error
- .long 97b,dst_error
+ .section __ex_table,"a"
+ .align 2
+ .long 70b,src_error
+ .long 71b,dst_error
+ .long 72b,src_error
+ .long 73b,dst_error
+ .long 54b,dst_error
+ .text
+
+/*
+ * this stuff handles faults in the cacheline loop and branches to either
+ * src_error (if in read part) or dst_error (if in write part)
+ */
+ CSUM_COPY_16_BYTES_EXCODE(0)
+#if L1_CACHE_BYTES >= 32
+ CSUM_COPY_16_BYTES_EXCODE(1)
+#if L1_CACHE_BYTES >= 64
+ CSUM_COPY_16_BYTES_EXCODE(2)
+ CSUM_COPY_16_BYTES_EXCODE(3)
+#if L1_CACHE_BYTES >= 128
+ CSUM_COPY_16_BYTES_EXCODE(4)
+ CSUM_COPY_16_BYTES_EXCODE(5)
+ CSUM_COPY_16_BYTES_EXCODE(6)
+ CSUM_COPY_16_BYTES_EXCODE(7)
+#endif
+#endif
+#endif
+
+ .section __ex_table,"a"
+ .align 2
+ .long 30b,src_error
+ .long 31b,dst_error
+ .long 40b,src_error
+ .long 41b,dst_error
+ .long 50b,src_error
+ .long 51b,dst_error
--
2.1.0

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Next message: Christophe Leroy: "[PATCH 1/2] powerpc32: checksum_wrappers_64 becomes checksum_wrappers"
Previous message: Dan Williams: "Re: [PATCH 14/15] libnvdimm: support read-only btt backing devices"
In reply to: Christophe Leroy: "[PATCH 0/2] powerpc32: optimisation of csum_partial_copy_generic()"
Next in thread: Christophe Leroy: "[PATCH 1/2] powerpc32: checksum_wrappers_64 becomes checksum_wrappers"
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