From 23b7576d7879cdc93e3328e1a9228e8843780012 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Tue, 11 Oct 2022 17:55:51 -0400 Subject: [PATCH] migration: Use atomic ops properly for page accountings To prepare for thread-safety on page accountings, at least below counters need to be accessed only atomically, they are: ram_counters.transferred ram_counters.duplicate ram_counters.normal ram_counters.postcopy_bytes There are a lot of other counters but they won't be accessed outside migration thread, then they're still safe to be accessed without atomic ops. Reviewed-by: Dr. David Alan Gilbert Signed-off-by: Peter Xu Reviewed-by: Juan Quintela Signed-off-by: Juan Quintela --- migration/migration.c | 10 +++++----- migration/multifd.c | 4 ++-- migration/ram.c | 40 ++++++++++++++++++++++++---------------- migration/ram.h | 20 ++++++++++++++++++++ 4 files changed, 51 insertions(+), 23 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index f485eea5fb..de83c50f51 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1049,13 +1049,13 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s) info->has_ram = true; info->ram = g_malloc0(sizeof(*info->ram)); - info->ram->transferred = ram_counters.transferred; + info->ram->transferred = stat64_get(&ram_atomic_counters.transferred); info->ram->total = ram_bytes_total(); - info->ram->duplicate = ram_counters.duplicate; + info->ram->duplicate = stat64_get(&ram_atomic_counters.duplicate); /* legacy value. It is not used anymore */ info->ram->skipped = 0; - info->ram->normal = ram_counters.normal; - info->ram->normal_bytes = ram_counters.normal * page_size; + info->ram->normal = stat64_get(&ram_atomic_counters.normal); + info->ram->normal_bytes = info->ram->normal * page_size; info->ram->mbps = s->mbps; info->ram->dirty_sync_count = ram_counters.dirty_sync_count; info->ram->dirty_sync_missed_zero_copy = @@ -1066,7 +1066,7 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s) info->ram->pages_per_second = s->pages_per_second; info->ram->precopy_bytes = ram_counters.precopy_bytes; info->ram->downtime_bytes = ram_counters.downtime_bytes; - info->ram->postcopy_bytes = ram_counters.postcopy_bytes; + info->ram->postcopy_bytes = stat64_get(&ram_atomic_counters.postcopy_bytes); if (migrate_use_xbzrle()) { info->has_xbzrle_cache = true; diff --git a/migration/multifd.c b/migration/multifd.c index b8dc559d24..000ca4d4ec 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -432,7 +432,7 @@ static int multifd_send_pages(QEMUFile *f) transferred = ((uint64_t) pages->num) * p->page_size + p->packet_len; qemu_file_acct_rate_limit(f, transferred); ram_counters.multifd_bytes += transferred; - ram_counters.transferred += transferred; + stat64_add(&ram_atomic_counters.transferred, transferred); qemu_mutex_unlock(&p->mutex); qemu_sem_post(&p->sem); @@ -624,7 +624,7 @@ int multifd_send_sync_main(QEMUFile *f) p->pending_job++; qemu_file_acct_rate_limit(f, p->packet_len); ram_counters.multifd_bytes += p->packet_len; - ram_counters.transferred += p->packet_len; + stat64_add(&ram_atomic_counters.transferred, p->packet_len); qemu_mutex_unlock(&p->mutex); qemu_sem_post(&p->sem); diff --git a/migration/ram.c b/migration/ram.c index 5379164749..f4cd9038f4 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -425,18 +425,25 @@ uint64_t ram_bytes_remaining(void) 0; } +/* + * NOTE: not all stats in ram_counters are used in reality. See comments + * for struct MigrationAtomicStats. The ultimate result of ram migration + * counters will be a merged version with both ram_counters and the atomic + * fields in ram_atomic_counters. + */ MigrationStats ram_counters; +MigrationAtomicStats ram_atomic_counters; void ram_transferred_add(uint64_t bytes) { if (runstate_is_running()) { ram_counters.precopy_bytes += bytes; } else if (migration_in_postcopy()) { - ram_counters.postcopy_bytes += bytes; + stat64_add(&ram_atomic_counters.postcopy_bytes, bytes); } else { ram_counters.downtime_bytes += bytes; } - ram_counters.transferred += bytes; + stat64_add(&ram_atomic_counters.transferred, bytes); } void dirty_sync_missed_zero_copy(void) @@ -725,7 +732,7 @@ void mig_throttle_counter_reset(void) rs->time_last_bitmap_sync = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); rs->num_dirty_pages_period = 0; - rs->bytes_xfer_prev = ram_counters.transferred; + rs->bytes_xfer_prev = stat64_get(&ram_atomic_counters.transferred); } /** @@ -1085,8 +1092,9 @@ uint64_t ram_pagesize_summary(void) uint64_t ram_get_total_transferred_pages(void) { - return ram_counters.normal + ram_counters.duplicate + - compression_counters.pages + xbzrle_counters.pages; + return stat64_get(&ram_atomic_counters.normal) + + stat64_get(&ram_atomic_counters.duplicate) + + compression_counters.pages + xbzrle_counters.pages; } static void migration_update_rates(RAMState *rs, int64_t end_time) @@ -1145,8 +1153,8 @@ static void migration_trigger_throttle(RAMState *rs) { MigrationState *s = migrate_get_current(); uint64_t threshold = s->parameters.throttle_trigger_threshold; - - uint64_t bytes_xfer_period = ram_counters.transferred - rs->bytes_xfer_prev; + uint64_t bytes_xfer_period = + stat64_get(&ram_atomic_counters.transferred) - rs->bytes_xfer_prev; uint64_t bytes_dirty_period = rs->num_dirty_pages_period * TARGET_PAGE_SIZE; uint64_t bytes_dirty_threshold = bytes_xfer_period * threshold / 100; @@ -1209,7 +1217,7 @@ static void migration_bitmap_sync(RAMState *rs) /* reset period counters */ rs->time_last_bitmap_sync = end_time; rs->num_dirty_pages_period = 0; - rs->bytes_xfer_prev = ram_counters.transferred; + rs->bytes_xfer_prev = stat64_get(&ram_atomic_counters.transferred); } if (migrate_use_events()) { qapi_event_send_migration_pass(ram_counters.dirty_sync_count); @@ -1285,7 +1293,7 @@ static int save_zero_page(RAMState *rs, RAMBlock *block, ram_addr_t offset) int len = save_zero_page_to_file(rs, rs->f, block, offset); if (len) { - ram_counters.duplicate++; + stat64_add(&ram_atomic_counters.duplicate, 1); ram_transferred_add(len); return 1; } @@ -1322,9 +1330,9 @@ static bool control_save_page(RAMState *rs, RAMBlock *block, ram_addr_t offset, } if (bytes_xmit > 0) { - ram_counters.normal++; + stat64_add(&ram_atomic_counters.normal, 1); } else if (bytes_xmit == 0) { - ram_counters.duplicate++; + stat64_add(&ram_atomic_counters.duplicate, 1); } return true; @@ -1354,7 +1362,7 @@ static int save_normal_page(RAMState *rs, RAMBlock *block, ram_addr_t offset, qemu_put_buffer(rs->f, buf, TARGET_PAGE_SIZE); } ram_transferred_add(TARGET_PAGE_SIZE); - ram_counters.normal++; + stat64_add(&ram_atomic_counters.normal, 1); return 1; } @@ -1410,7 +1418,7 @@ static int ram_save_multifd_page(RAMState *rs, RAMBlock *block, if (multifd_queue_page(rs->f, block, offset) < 0) { return -1; } - ram_counters.normal++; + stat64_add(&ram_atomic_counters.normal, 1); return 1; } @@ -1448,7 +1456,7 @@ update_compress_thread_counts(const CompressParam *param, int bytes_xmit) ram_transferred_add(bytes_xmit); if (param->zero_page) { - ram_counters.duplicate++; + stat64_add(&ram_atomic_counters.duplicate, 1); return; } @@ -2623,9 +2631,9 @@ void acct_update_position(QEMUFile *f, size_t size, bool zero) uint64_t pages = size / TARGET_PAGE_SIZE; if (zero) { - ram_counters.duplicate += pages; + stat64_add(&ram_atomic_counters.duplicate, pages); } else { - ram_counters.normal += pages; + stat64_add(&ram_atomic_counters.normal, pages); ram_transferred_add(size); qemu_file_credit_transfer(f, size); } diff --git a/migration/ram.h b/migration/ram.h index 038d52f49f..81cbb0947c 100644 --- a/migration/ram.h +++ b/migration/ram.h @@ -32,7 +32,27 @@ #include "qapi/qapi-types-migration.h" #include "exec/cpu-common.h" #include "io/channel.h" +#include "qemu/stats64.h" +/* + * These are the migration statistic counters that need to be updated using + * atomic ops (can be accessed by more than one thread). Here since we + * cannot modify MigrationStats directly to use Stat64 as it was defined in + * the QAPI scheme, we define an internal structure to hold them, and we + * propagate the real values when QMP queries happen. + * + * IOW, the corresponding fields within ram_counters on these specific + * fields will be always zero and not being used at all; they're just + * placeholders to make it QAPI-compatible. + */ +typedef struct { + Stat64 transferred; + Stat64 duplicate; + Stat64 normal; + Stat64 postcopy_bytes; +} MigrationAtomicStats; + +extern MigrationAtomicStats ram_atomic_counters; extern MigrationStats ram_counters; extern XBZRLECacheStats xbzrle_counters; extern CompressionStats compression_counters; -- 2.39.2