From 87f3bd8717cd88932de302e215f1da51bfb8051a Mon Sep 17 00:00:00 2001 From: Ivan Ren Date: Fri, 2 Aug 2019 18:18:41 +0800 Subject: [PATCH] migration: always initialise ram_counters for a new migration This patch fix a multifd migration bug in migration speed calculation, this problem can be reproduced as follows: 1. start a vm and give a heavy memory write stress to prevent the vm be successfully migrated to destination 2. begin a migration with multifd 3. migrate for a long time [actually, this can be measured by transferred bytes] 4. migrate cancel 5. begin a new migration with multifd, the migration will directly run into migration_completion phase Reason as follows: Migration update bandwidth and s->threshold_size in function migration_update_counters after BUFFER_DELAY time: current_bytes = migration_total_bytes(s); transferred = current_bytes - s->iteration_initial_bytes; time_spent = current_time - s->iteration_start_time; bandwidth = (double)transferred / time_spent; s->threshold_size = bandwidth * s->parameters.downtime_limit; In multifd migration, migration_total_bytes function return qemu_ftell(s->to_dst_file) + ram_counters.multifd_bytes. s->iteration_initial_bytes will be initialized to 0 at every new migration, but ram_counters is a global variable, and history migration data will be accumulated. So if the ram_counters.multifd_bytes is big enough, it may lead pending_size >= s->threshold_size become false in migration_iteration_run after the first migration_update_counters. Signed-off-by: Ivan Ren Reviewed-by: Juan Quintela Reviewed-by: Wei Yang Suggested-by: Wei Yang Message-Id: <1564741121-1840-1-git-send-email-ivanren@tencent.com> Signed-off-by: Dr. David Alan Gilbert --- migration/migration.c | 25 +++++++++++++++++++------ migration/savevm.c | 1 + 2 files changed, 20 insertions(+), 6 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index 12b8e5dbe5..c49e9dc035 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1911,6 +1911,11 @@ static bool migrate_prepare(MigrationState *s, bool blk, bool blk_inc, } migrate_init(s); + /* + * set ram_counters memory to zero for a + * new migration + */ + memset(&ram_counters, 0, sizeof(ram_counters)); return true; } @@ -3034,6 +3039,17 @@ static void migration_calculate_complete(MigrationState *s) } } +static void update_iteration_initial_status(MigrationState *s) +{ + /* + * Update these three fields at the same time to avoid mismatch info lead + * wrong speed calculation. + */ + s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); + s->iteration_initial_bytes = migration_total_bytes(s); + s->iteration_initial_pages = ram_get_total_transferred_pages(); +} + static void migration_update_counters(MigrationState *s, int64_t current_time) { @@ -3069,9 +3085,7 @@ static void migration_update_counters(MigrationState *s, qemu_file_reset_rate_limit(s->to_dst_file); - s->iteration_start_time = current_time; - s->iteration_initial_bytes = current_bytes; - s->iteration_initial_pages = ram_get_total_transferred_pages(); + update_iteration_initial_status(s); trace_migrate_transferred(transferred, time_spent, bandwidth, s->threshold_size); @@ -3194,7 +3208,7 @@ static void *migration_thread(void *opaque) rcu_register_thread(); object_ref(OBJECT(s)); - s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); + update_iteration_initial_status(s); qemu_savevm_state_header(s->to_dst_file); @@ -3259,8 +3273,7 @@ static void *migration_thread(void *opaque) * the local variables. This is important to avoid * breaking transferred_bytes and bandwidth calculation */ - s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); - s->iteration_initial_bytes = 0; + update_iteration_initial_status(s); } current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); diff --git a/migration/savevm.c b/migration/savevm.c index 412768216c..1ac15301ad 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -1456,6 +1456,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp) } migrate_init(ms); + memset(&ram_counters, 0, sizeof(ram_counters)); ms->to_dst_file = f; qemu_mutex_unlock_iothread();