From 04ffce137b6d85ab4e7687e54e4dffcef0a9ab99 Mon Sep 17 00:00:00 2001 From: ling xu Date: Wed, 16 Nov 2022 23:29:22 +0800 Subject: AVX512 support for xbzrle_encode_buffer This commit is the same with [PATCH v6 1/2], and provides avx512 support for xbzrle_encode_buffer function to accelerate xbzrle encoding speed. Runtime check of avx512 support and benchmark for this feature are added. Compared with C version of xbzrle_encode_buffer function, avx512 version can achieve 50%-70% performance improvement on benchmarking. In addition, if dirty data is randomly located in 4K page, the avx512 version can achieve almost 140% performance gain. Signed-off-by: ling xu Co-authored-by: Zhou Zhao Co-authored-by: Jun Jin Reviewed-by: Juan Quintela Signed-off-by: Juan Quintela --- migration/ram.c | 34 +++++++++++++-- migration/xbzrle.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++++ migration/xbzrle.h | 4 ++ 3 files changed, 159 insertions(+), 3 deletions(-) (limited to 'migration') diff --git a/migration/ram.c b/migration/ram.c index 0890816..18ac68b 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -83,6 +83,34 @@ /* 0x80 is reserved in migration.h start with 0x100 next */ #define RAM_SAVE_FLAG_COMPRESS_PAGE 0x100 +int (*xbzrle_encode_buffer_func)(uint8_t *, uint8_t *, int, + uint8_t *, int) = xbzrle_encode_buffer; +#if defined(CONFIG_AVX512BW_OPT) +#include "qemu/cpuid.h" +static void __attribute__((constructor)) init_cpu_flag(void) +{ + unsigned max = __get_cpuid_max(0, NULL); + int a, b, c, d; + if (max >= 1) { + __cpuid(1, a, b, c, d); + /* We must check that AVX is not just available, but usable. */ + if ((c & bit_OSXSAVE) && (c & bit_AVX) && max >= 7) { + int bv; + __asm("xgetbv" : "=a"(bv), "=d"(d) : "c"(0)); + __cpuid_count(7, 0, a, b, c, d); + /* 0xe6: + * XCR0[7:5] = 111b (OPMASK state, upper 256-bit of ZMM0-ZMM15 + * and ZMM16-ZMM31 state are enabled by OS) + * XCR0[2:1] = 11b (XMM state and YMM state are enabled by OS) + */ + if ((bv & 0xe6) == 0xe6 && (b & bit_AVX512BW)) { + xbzrle_encode_buffer_func = xbzrle_encode_buffer_avx512; + } + } + } +} +#endif + XBZRLECacheStats xbzrle_counters; /* used by the search for pages to send */ @@ -806,9 +834,9 @@ static int save_xbzrle_page(RAMState *rs, PageSearchStatus *pss, memcpy(XBZRLE.current_buf, *current_data, TARGET_PAGE_SIZE); /* XBZRLE encoding (if there is no overflow) */ - encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf, - TARGET_PAGE_SIZE, XBZRLE.encoded_buf, - TARGET_PAGE_SIZE); + encoded_len = xbzrle_encode_buffer_func(prev_cached_page, XBZRLE.current_buf, + TARGET_PAGE_SIZE, XBZRLE.encoded_buf, + TARGET_PAGE_SIZE); /* * Update the cache contents, so that it corresponds to the data diff --git a/migration/xbzrle.c b/migration/xbzrle.c index 1ba482d..05366e8 100644 --- a/migration/xbzrle.c +++ b/migration/xbzrle.c @@ -174,3 +174,127 @@ int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen) return d; } + +#if defined(CONFIG_AVX512BW_OPT) +#pragma GCC push_options +#pragma GCC target("avx512bw") +#include +int xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen, + uint8_t *dst, int dlen) +{ + uint32_t zrun_len = 0, nzrun_len = 0; + int d = 0, i = 0, num = 0; + uint8_t *nzrun_start = NULL; + /* add 1 to include residual part in main loop */ + uint32_t count512s = (slen >> 6) + 1; + /* countResidual is tail of data, i.e., countResidual = slen % 64 */ + uint32_t count_residual = slen & 0b111111; + bool never_same = true; + uint64_t mask_residual = 1; + mask_residual <<= count_residual; + mask_residual -= 1; + __m512i r = _mm512_set1_epi32(0); + + while (count512s) { + if (d + 2 > dlen) { + return -1; + } + + int bytes_to_check = 64; + uint64_t mask = 0xffffffffffffffff; + if (count512s == 1) { + bytes_to_check = count_residual; + mask = mask_residual; + } + __m512i old_data = _mm512_mask_loadu_epi8(r, + mask, old_buf + i); + __m512i new_data = _mm512_mask_loadu_epi8(r, + mask, new_buf + i); + uint64_t comp = _mm512_cmpeq_epi8_mask(old_data, new_data); + count512s--; + + bool is_same = (comp & 0x1); + while (bytes_to_check) { + if (is_same) { + if (nzrun_len) { + d += uleb128_encode_small(dst + d, nzrun_len); + if (d + nzrun_len > dlen) { + return -1; + } + nzrun_start = new_buf + i - nzrun_len; + memcpy(dst + d, nzrun_start, nzrun_len); + d += nzrun_len; + nzrun_len = 0; + } + /* 64 data at a time for speed */ + if (count512s && (comp == 0xffffffffffffffff)) { + i += 64; + zrun_len += 64; + break; + } + never_same = false; + num = __builtin_ctzll(~comp); + num = (num < bytes_to_check) ? num : bytes_to_check; + zrun_len += num; + bytes_to_check -= num; + comp >>= num; + i += num; + if (bytes_to_check) { + /* still has different data after same data */ + d += uleb128_encode_small(dst + d, zrun_len); + zrun_len = 0; + } else { + break; + } + } + if (never_same || zrun_len) { + /* + * never_same only acts if + * data begins with diff in first count512s + */ + d += uleb128_encode_small(dst + d, zrun_len); + zrun_len = 0; + never_same = false; + } + /* has diff, 64 data at a time for speed */ + if ((bytes_to_check == 64) && (comp == 0x0)) { + i += 64; + nzrun_len += 64; + break; + } + num = __builtin_ctzll(comp); + num = (num < bytes_to_check) ? num : bytes_to_check; + nzrun_len += num; + bytes_to_check -= num; + comp >>= num; + i += num; + if (bytes_to_check) { + /* mask like 111000 */ + d += uleb128_encode_small(dst + d, nzrun_len); + /* overflow */ + if (d + nzrun_len > dlen) { + return -1; + } + nzrun_start = new_buf + i - nzrun_len; + memcpy(dst + d, nzrun_start, nzrun_len); + d += nzrun_len; + nzrun_len = 0; + is_same = true; + } + } + } + + if (nzrun_len != 0) { + d += uleb128_encode_small(dst + d, nzrun_len); + /* overflow */ + if (d + nzrun_len > dlen) { + return -1; + } + nzrun_start = new_buf + i - nzrun_len; + memcpy(dst + d, nzrun_start, nzrun_len); + d += nzrun_len; + } + return d; +} +#pragma GCC pop_options +#endif diff --git a/migration/xbzrle.h b/migration/xbzrle.h index a0db507..6feb491 100644 --- a/migration/xbzrle.h +++ b/migration/xbzrle.h @@ -18,4 +18,8 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen, uint8_t *dst, int dlen); int xbzrle_decode_buffer(uint8_t *src, int slen, uint8_t *dst, int dlen); +#if defined(CONFIG_AVX512BW_OPT) +int xbzrle_encode_buffer_avx512(uint8_t *old_buf, uint8_t *new_buf, int slen, + uint8_t *dst, int dlen); +#endif #endif -- cgit v1.1