migration/calc-dirty-rate: replaced CRC32 with xxHash
This significantly reduces overhead of dirty page rate calculation in sampling mode. Tested using 32GiB VM on E5-2690 CPU. With CRC32: total_pages=8388608 sampled_pages=16384 millis=71 With xxHash: total_pages=8388608 sampled_pages=16384 millis=14 Signed-off-by: Andrei Gudkov <gudkov.andrei@huawei.com> Message-Id: <cd115a89fc81d5f2eeb4ea7d57a98b84f794f340.1682598010.git.gudkov.andrei@huawei.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>
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@ -29,6 +29,7 @@
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#include "sysemu/kvm.h"
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#include "sysemu/runstate.h"
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#include "exec/memory.h"
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#include "qemu/xxhash.h"
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/*
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* total_dirty_pages is procted by BQL and is used
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@ -308,6 +309,33 @@ static void update_dirtyrate(uint64_t msec)
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DirtyStat.dirty_rate = dirtyrate;
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}
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/*
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* Compute hash of a single page of size TARGET_PAGE_SIZE.
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*/
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static uint32_t compute_page_hash(void *ptr)
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{
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uint32_t i;
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uint64_t v1, v2, v3, v4;
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uint64_t res;
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const uint64_t *p = ptr;
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v1 = QEMU_XXHASH_SEED + XXH_PRIME64_1 + XXH_PRIME64_2;
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v2 = QEMU_XXHASH_SEED + XXH_PRIME64_2;
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v3 = QEMU_XXHASH_SEED + 0;
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v4 = QEMU_XXHASH_SEED - XXH_PRIME64_1;
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for (i = 0; i < TARGET_PAGE_SIZE / 8; i += 4) {
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v1 = XXH64_round(v1, p[i + 0]);
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v2 = XXH64_round(v2, p[i + 1]);
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v3 = XXH64_round(v3, p[i + 2]);
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v4 = XXH64_round(v4, p[i + 3]);
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}
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res = XXH64_mergerounds(v1, v2, v3, v4);
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res += TARGET_PAGE_SIZE;
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res = XXH64_avalanche(res);
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return (uint32_t)(res & UINT32_MAX);
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}
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/*
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* get hash result for the sampled memory with length of TARGET_PAGE_SIZE
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* in ramblock, which starts from ramblock base address.
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@ -315,13 +343,12 @@ static void update_dirtyrate(uint64_t msec)
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static uint32_t get_ramblock_vfn_hash(struct RamblockDirtyInfo *info,
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uint64_t vfn)
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{
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uint32_t crc;
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uint32_t hash;
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crc = crc32(0, (info->ramblock_addr +
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vfn * TARGET_PAGE_SIZE), TARGET_PAGE_SIZE);
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hash = compute_page_hash(info->ramblock_addr + vfn * TARGET_PAGE_SIZE);
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trace_get_ramblock_vfn_hash(info->idstr, vfn, crc);
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return crc;
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trace_get_ramblock_vfn_hash(info->idstr, vfn, hash);
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return hash;
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}
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static bool save_ramblock_hash(struct RamblockDirtyInfo *info)
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@ -454,13 +481,13 @@ out:
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static void calc_page_dirty_rate(struct RamblockDirtyInfo *info)
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{
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uint32_t crc;
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uint32_t hash;
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int i;
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for (i = 0; i < info->sample_pages_count; i++) {
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crc = get_ramblock_vfn_hash(info, info->sample_page_vfn[i]);
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if (crc != info->hash_result[i]) {
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trace_calc_page_dirty_rate(info->idstr, crc, info->hash_result[i]);
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hash = get_ramblock_vfn_hash(info, info->sample_page_vfn[i]);
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if (hash != info->hash_result[i]) {
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trace_calc_page_dirty_rate(info->idstr, hash, info->hash_result[i]);
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info->sample_dirty_count++;
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}
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}
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@ -342,8 +342,8 @@ dirty_bitmap_load_success(void) ""
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# dirtyrate.c
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dirtyrate_set_state(const char *new_state) "new state %s"
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query_dirty_rate_info(const char *new_state) "current state %s"
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get_ramblock_vfn_hash(const char *idstr, uint64_t vfn, uint32_t crc) "ramblock name: %s, vfn: %"PRIu64 ", crc: %" PRIu32
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calc_page_dirty_rate(const char *idstr, uint32_t new_crc, uint32_t old_crc) "ramblock name: %s, new crc: %" PRIu32 ", old crc: %" PRIu32
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get_ramblock_vfn_hash(const char *idstr, uint64_t vfn, uint32_t hash) "ramblock name: %s, vfn: %"PRIu64 ", hash: %" PRIu32
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calc_page_dirty_rate(const char *idstr, uint32_t new_hash, uint32_t old_hash) "ramblock name: %s, new hash: %" PRIu32 ", old hash: %" PRIu32
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skip_sample_ramblock(const char *idstr, uint64_t ramblock_size) "ramblock name: %s, ramblock size: %" PRIu64
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find_page_matched(const char *idstr) "ramblock %s addr or size changed"
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dirtyrate_calculate(int64_t dirtyrate) "dirty rate: %" PRIi64 " MB/s"
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