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X-Received-From: 2607:f8b0:4864:20::542 Subject: [Qemu-devel] [PATCH v3] migration: always initial ram_counters for a new migration X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: richardw.yang@linux.intel.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Ivan Ren 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 b= ytes] 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 =3D migration_total_bytes(s); transferred =3D current_bytes - s->iteration_initial_bytes; time_spent =3D current_time - s->iteration_start_time; bandwidth =3D (double)transferred / time_spent; s->threshold_size =3D 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 >=3D s->threshold_size become false in migration_iteration_run after the first migration_update_counters. Signed-off-by: Ivan Ren Reviewed-by: Juan Quintela Suggested-by: Wei Yang Reviewed-by: Wei Yang --- v2->v3: - fix the bug of update_iteration_initial_status function prototype v1->v2: - Add interface update_iteration_initial_status to update statistic fields at the same time to avoid info mismatch lead wrong calculation result. 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 8a607fe1e2..bea9b1d796 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1908,6 +1908,11 @@ static bool migrate_prepare(MigrationState *s, bool = blk, bool blk_inc, } =20 migrate_init(s); + /* + * set ram_counters memory to zero for a + * new migration + */ + memset(&ram_counters, 0, sizeof(ram_counters)); =20 return true; } @@ -3025,6 +3030,17 @@ static void migration_calculate_complete(MigrationSt= ate *s) } } =20 +static void update_iteration_initial_status(MigrationState *s) +{ + /* + * Update these three fields at the same time to avoid mismatch info l= ead + * wrong speed calculation. + */ + s->iteration_start_time =3D qemu_clock_get_ms(QEMU_CLOCK_REALTIME); + s->iteration_initial_bytes =3D migration_total_bytes(s); + s->iteration_initial_pages =3D ram_get_total_transferred_pages(); +} + static void migration_update_counters(MigrationState *s, int64_t current_time) { @@ -3060,9 +3076,7 @@ static void migration_update_counters(MigrationState = *s, =20 qemu_file_reset_rate_limit(s->to_dst_file); =20 - s->iteration_start_time =3D current_time; - s->iteration_initial_bytes =3D current_bytes; - s->iteration_initial_pages =3D ram_get_total_transferred_pages(); + update_iteration_initial_status(s); =20 trace_migrate_transferred(transferred, time_spent, bandwidth, s->threshold_size); @@ -3186,7 +3200,7 @@ static void *migration_thread(void *opaque) rcu_register_thread(); =20 object_ref(OBJECT(s)); - s->iteration_start_time =3D qemu_clock_get_ms(QEMU_CLOCK_REALTIME); + update_iteration_initial_status(s); =20 qemu_savevm_state_header(s->to_dst_file); =20 @@ -3251,8 +3265,7 @@ static void *migration_thread(void *opaque) * the local variables. This is important to avoid * breaking transferred_bytes and bandwidth calculation */ - s->iteration_start_time =3D qemu_clock_get_ms(QEMU_CLOCK_REALT= IME); - s->iteration_initial_bytes =3D 0; + update_iteration_initial_status(s); } =20 current_time =3D qemu_clock_get_ms(QEMU_CLOCK_REALTIME); diff --git a/migration/savevm.c b/migration/savevm.c index 79ed44d475..480c511b19 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -1424,6 +1424,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **err= p) } =20 migrate_init(ms); + memset(&ram_counters, 0, sizeof(ram_counters)); ms->to_dst_file =3D f; =20 qemu_mutex_unlock_iothread(); --=20 2.17.2 (Apple Git-113)