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[PATCH v4 1/2] Update AVX512 support for xbzrle_encode_buffer function
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From: |
ling xu |
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Subject: |
[PATCH v4 1/2] Update AVX512 support for xbzrle_encode_buffer function |
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Date: |
Tue, 9 Aug 2022 16:32:48 +0800 |
This commit update code of avx512 support for xbzrle_encode_buffer
function to accelerate xbzrle encoding speed.
Compared with C version of xbzrle_encode_buffer function, avx512 version
can achieve almost 60%-70% performance improvement on unit test provided
by Qemu. In addition, we provide one more unit test called
"test_encode_decode_random_avx512", in which dirty data are randomly
located in 4K page, and this case can achieve almost 140% performance
gain.
Signed-off-by: ling xu <ling1.xu@intel.com>
Co-authored-by: Zhou Zhao <zhou.zhao@intel.com>
Co-authored-by: Jun Jin <jun.i.jin@intel.com>
---
meson.build | 16 ++++
meson_options.txt | 2 +
migration/ram.c | 42 ++++++++++-
migration/xbzrle.c | 181 +++++++++++++++++++++++++++++++++++++++++++++
migration/xbzrle.h | 4 +
5 files changed, 242 insertions(+), 3 deletions(-)
diff --git a/meson.build b/meson.build
index 294e9a8f32..4222b77e9f 100644
--- a/meson.build
+++ b/meson.build
@@ -2262,6 +2262,22 @@ config_host_data.set('CONFIG_AVX512F_OPT',
get_option('avx512f') \
int main(int argc, char *argv[]) { return bar(argv[0]); }
'''), error_message: 'AVX512F not available').allowed())
+config_host_data.set('CONFIG_AVX512BW_OPT', get_option('avx512bw') \
+ .require(have_cpuid_h, error_message: 'cpuid.h not available, cannot enable
AVX512BW') \
+ .require(cc.links('''
+ #pragma GCC push_options
+ #pragma GCC target("avx512bw")
+ #include <cpuid.h>
+ #include <immintrin.h>
+ static int bar(void *a) {
+
+ __m512i x = *(__m512i *)a;
+ __m512i res= _mm512_abs_epi8(x);
+ return res[1];
+ }
+ int main(int argc, char *argv[]) { return bar(argv[0]); }
+ '''), error_message: 'AVX512BW not available').allowed())
+
have_pvrdma = get_option('pvrdma') \
.require(rdma.found(), error_message: 'PVRDMA requires OpenFabrics
libraries') \
.require(cc.compiles(gnu_source_prefix + '''
diff --git a/meson_options.txt b/meson_options.txt
index e58e158396..07194bf680 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -104,6 +104,8 @@ option('avx2', type: 'feature', value: 'auto',
description: 'AVX2 optimizations')
option('avx512f', type: 'feature', value: 'disabled',
description: 'AVX512F optimizations')
+option('avx512bw', type: 'feature', value: 'auto',
+ description: 'AVX512BW optimizations')
option('keyring', type: 'feature', value: 'auto',
description: 'Linux keyring support')
diff --git a/migration/ram.c b/migration/ram.c
index dc1de9ddbc..bae7bef236 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -83,6 +83,35 @@
/* 0x80 is reserved in migration.h start with 0x100 next */
#define RAM_SAVE_FLAG_COMPRESS_PAGE 0x100
+#if defined(CONFIG_AVX512BW_OPT)
+static bool is_cpu_support_avx512bw;
+#include "qemu/cpuid.h"
+static void __attribute__((constructor)) init_cpu_flag(void)
+{
+ unsigned max = __get_cpuid_max(0, NULL);
+ int a, b, c, d;
+ is_cpu_support_avx512bw = false;
+ 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)) {
+ is_cpu_support_avx512bw = true;
+ }
+ }
+ }
+ return ;
+}
+#endif
+
XBZRLECacheStats xbzrle_counters;
/* struct contains XBZRLE cache and a static page
@@ -802,9 +831,16 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
**current_data,
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);
+ int (*xbzrle_encode_buffer_func)(uint8_t *, uint8_t *, int,
+ uint8_t *, int) = xbzrle_encode_buffer;
+ #if defined(CONFIG_AVX512BW_OPT)
+ if (likely(is_cpu_support_avx512bw)) {
+ xbzrle_encode_buffer_func = xbzrle_encode_buffer_avx512;
+ }
+ #endif
+ 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 1ba482ded9..804adc1acb 100644
--- a/migration/xbzrle.c
+++ b/migration/xbzrle.c
@@ -174,3 +174,184 @@ 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 <immintrin.h>
+#include <math.h>
+#define SET_ZERO512(r) r = _mm512_set1_epi32(0)
+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;
+ int count512s = (slen >> 6);
+ int countResidual = slen % 64;
+ bool never_same = true;
+ while (count512s--) {
+ if (d + 2 > dlen) {
+ return -1;
+ }
+ __m512i old_data = _mm512_mask_loadu_epi8(old_data,
+ 0xffffffffffffffff, old_buf + i);
+ __m512i new_data = _mm512_mask_loadu_epi8(new_data,
+ 0xffffffffffffffff, new_buf +
i);
+ /* in mask bit 1 for same, 0 for diff */
+ __mmask64 comp = _mm512_cmpeq_epi8_mask(old_data, new_data);
+
+ int bytesToCheck = 64;
+ bool is_same = (comp & 0x1);
+ while (bytesToCheck) {
+ 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;
+ }
+ if (comp == 0xffffffffffffffff) {
+ i += 64;
+ zrun_len += 64;
+ break;
+ }
+ never_same = false;
+ num = __builtin_ctzl(~comp);
+ num = (num < bytesToCheck) ? num : bytesToCheck;
+ zrun_len += num;
+ bytesToCheck -= num;
+ comp >>= num;
+ i += num;
+ if (bytesToCheck) {
+ /* 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 */
+ if ((bytesToCheck == 64) && (comp == 0x0)) {
+ i += 64;
+ nzrun_len += 64;
+ break;
+ }
+ num = __builtin_ctzl(comp);
+ num = (num < bytesToCheck) ? num : bytesToCheck;
+ nzrun_len += num;
+ bytesToCheck -= num;
+ comp >>= num;
+ i += num;
+ if (bytesToCheck) {
+ /* 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 (countResidual) {
+ /* the number of data is less than 64 */
+ uint64_t mask = pow(2, countResidual);
+ mask -= 1;
+ __m512i r = SET_ZERO512(r);
+ __m512i old_data = _mm512_mask_loadu_epi8(r, mask, old_buf + i);
+ __m512i new_data = _mm512_mask_loadu_epi8(r, mask, new_buf + i);
+ __mmask64 comp = _mm512_cmpeq_epi8_mask(old_data, new_data);
+
+ int bytesToCheck = countResidual;
+ bool is_same = (comp & 0x1);
+ while (bytesToCheck) {
+ 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;
+ }
+ never_same = false;
+ num = __builtin_ctzl(~comp);
+ num = (num < bytesToCheck) ? num : bytesToCheck;
+ zrun_len += num;
+ bytesToCheck -= num;
+ comp >>= num;
+ i += num;
+ if (bytesToCheck) {
+ /* diff after same */
+ d += uleb128_encode_small(dst + d, zrun_len);
+ zrun_len = 0;
+ } else {
+ break;
+ }
+ }
+
+ if (never_same || zrun_len) {
+ d += uleb128_encode_small(dst + d, zrun_len);
+ zrun_len = 0;
+ never_same = false;
+ }
+ /* has diff */
+ num = __builtin_ctzl(comp);
+ num = (num < bytesToCheck) ? num : bytesToCheck;
+ nzrun_len += num;
+ bytesToCheck -= num;
+ comp >>= num;
+ i += num;
+ if (bytesToCheck) {
+ 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 (zrun_len) {
+ return (zrun_len == slen) ? 0 : d;
+ }
+ 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 a0db507b9c..6feb49160a 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
--
2.25.1