26293c89a6
Summary: Crc32c Parallel computation coding optimization: Macro unfolding removes the "for" loop and is good to decrease branch-miss in arm64 micro architecture 1024 Bytes is divided into 8(head) + 1008( 6 * 7 * 3 * 8 ) + 8(tail) three parts Macro unfolding 42 loops to 6 CRC32C7X24BYTESs 1 CRC32C7X24BYTES containing 7 CRC32C24BYTESs 1, crc32c_test [==========] Running 4 tests from 1 test case. [----------] Global test environment set-up. [----------] 4 tests from CRC [ RUN ] CRC.StandardResults [ OK ] CRC.StandardResults (1 ms) [ RUN ] CRC.Values [ OK ] CRC.Values (0 ms) [ RUN ] CRC.Extend [ OK ] CRC.Extend (0 ms) [ RUN ] CRC.Mask [ OK ] CRC.Mask (0 ms) [----------] 4 tests from CRC (1 ms total) [----------] Global test environment tear-down [==========] 4 tests from 1 test case ran. (1 ms total) [ PASSED ] 4 tests. 2, db_bench --benchmarks="crc32c" crc32c : 0.218 micros/op 4595390 ops/sec; 17950.7 MB/s (4096 per op) 3, repeated crc32c_test case 60000 times perf stat -e branch-miss -- ./crc32c_test before optimization: 739,426,504 branch-miss after optimization: 1,128,572 branch-miss Pull Request resolved: https://github.com/facebook/rocksdb/pull/5675 Differential Revision: D16989210 fbshipit-source-id: 7204e6069bb6ed066d49c2d1b3ac385065a98557
128 lines
3.2 KiB
C++
128 lines
3.2 KiB
C++
// Copyright (c) 2018, Arm Limited and affiliates. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#include "util/crc32c_arm64.h"
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#if defined(__linux__) && defined(HAVE_ARM64_CRC)
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#include <asm/hwcap.h>
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#include <sys/auxv.h>
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#ifndef HWCAP_CRC32
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#define HWCAP_CRC32 (1 << 7)
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#endif
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#ifdef HAVE_ARM64_CRYPTO
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/* unfolding to compute 8 * 3 = 24 bytes parallelly */
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#define CRC32C24BYTES(ITR) \
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crc1 = crc32c_u64(crc1, *(buf64 + BLK_LENGTH + (ITR)));\
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crc2 = crc32c_u64(crc2, *(buf64 + BLK_LENGTH*2 + (ITR)));\
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crc0 = crc32c_u64(crc0, *(buf64 + (ITR)));
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/* unfolding to compute 24 * 7 = 168 bytes parallelly */
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#define CRC32C7X24BYTES(ITR) do {\
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CRC32C24BYTES((ITR)*7+0) \
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CRC32C24BYTES((ITR)*7+1) \
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CRC32C24BYTES((ITR)*7+2) \
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CRC32C24BYTES((ITR)*7+3) \
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CRC32C24BYTES((ITR)*7+4) \
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CRC32C24BYTES((ITR)*7+5) \
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CRC32C24BYTES((ITR)*7+6) \
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} while(0)
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#endif
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uint32_t crc32c_runtime_check(void) {
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uint64_t auxv = getauxval(AT_HWCAP);
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return (auxv & HWCAP_CRC32) != 0;
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}
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uint32_t crc32c_arm64(uint32_t crc, unsigned char const *data,
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unsigned len) {
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const uint8_t *buf8;
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const uint64_t *buf64 = (uint64_t *)data;
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int length = (int)len;
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crc ^= 0xffffffff;
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#ifdef HAVE_ARM64_CRYPTO
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/* Crc32c Parallel computation
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* Algorithm comes from Intel whitepaper:
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* crc-iscsi-polynomial-crc32-instruction-paper
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*
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* Input data is divided into three equal-sized blocks
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* Three parallel blocks (crc0, crc1, crc2) for 1024 Bytes
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* One Block: 42(BLK_LENGTH) * 8(step length: crc32c_u64) bytes
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*/
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#define BLK_LENGTH 42
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while (length >= 1024) {
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uint64_t t0, t1;
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uint32_t crc0 = 0, crc1 = 0, crc2 = 0;
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/* Parallel Param:
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* k0 = CRC32(x ^ (42 * 8 * 8 * 2 - 1));
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* k1 = CRC32(x ^ (42 * 8 * 8 - 1));
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*/
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uint32_t k0 = 0xe417f38a, k1 = 0x8f158014;
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/* First 8 bytei for better pipelining */
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crc0 = crc32c_u64(crc, *buf64++);
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/* 3 blocks crc32c parallel computation
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* Macro unfolding to compute parallelly
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* 168 * 6 = 1008 (bytes)
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*/
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CRC32C7X24BYTES(0);
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CRC32C7X24BYTES(1);
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CRC32C7X24BYTES(2);
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CRC32C7X24BYTES(3);
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CRC32C7X24BYTES(4);
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CRC32C7X24BYTES(5);
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buf64 += (BLK_LENGTH * 3);
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/* Last 8 bytes */
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crc = crc32c_u64(crc2, *buf64++);
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t0 = (uint64_t)vmull_p64(crc0, k0);
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t1 = (uint64_t)vmull_p64(crc1, k1);
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/* Merge (crc0, crc1, crc2) -> crc */
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crc1 = crc32c_u64(0, t1);
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crc ^= crc1;
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crc0 = crc32c_u64(0, t0);
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crc ^= crc0;
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length -= 1024;
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}
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if (length == 0)
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return crc ^ (0xffffffffU);
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#endif
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buf8 = (const uint8_t *)buf64;
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while (length >= 8) {
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crc = crc32c_u64(crc, *(const uint64_t*)buf8);
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buf8 += 8;
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length -= 8;
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}
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/* The following is more efficient than the straight loop */
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if (length >= 4) {
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crc = crc32c_u32(crc, *(const uint32_t*)buf8);
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buf8 += 4;
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length -= 4;
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}
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if (length >= 2) {
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crc = crc32c_u16(crc, *(const uint16_t*)buf8);
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buf8 += 2;
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length -= 2;
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}
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if (length >= 1)
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crc = crc32c_u8(crc, *buf8);
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crc ^= 0xffffffff;
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return crc;
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}
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#endif
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