Commit 94f5a437 authored by Liang Li's avatar Liang Li Committed by Juan Quintela
Browse files

migration: defer migration_end & blk_mig_cleanup 



Because of the patch 3ea3b7fa9af067982f34b of kvm, which introduces a
lazy collapsing of small sptes into large sptes mechanism, now
migration_end() is a time consuming operation because it calls
memroy_global_dirty_log_stop(), which will trigger the dropping of small
sptes operation and takes about dozens of milliseconds, so call
migration_end() before all the vmsate data has already been transferred
to the destination will prolong VM downtime. This operation should be
deferred after all the data has been transferred to the destination.

blk_mig_cleanup() can be deferred too.

For a VM with 8G RAM, this patch can reduce the VM downtime about 30 ms.

Signed-off-by: default avatarLiang Li <liang.z.li@intel.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarJuan Quintela <quintela@redhat.com&gt;al3>
Reviewed-by: default avatarAmit Shah <amit.shah@redhat.com&gt;al3>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com&gt;al3>
parent 79cf9fad

migration/block.c

+0 −1
Original line number Diff line number Diff line
@@ -750,7 +750,6 @@ static int block_save_complete(QEMUFile *f, void *opaque) 


    qemu_put_be64(f, BLK_MIG_FLAG_EOS);



    blk_mig_cleanup();

    return 0;

}

migration/migration.c

+6 −7
Original line number Diff line number Diff line
@@ -613,13 +613,10 @@ static void migrate_fd_cleanup(void *opaque) 


    assert(s->state != MIGRATION_STATUS_ACTIVE);



    if (s->state != MIGRATION_STATUS_COMPLETED) {

        qemu_savevm_state_cancel();

    if (s->state == MIGRATION_STATUS_CANCELLING) {

        migrate_set_state(s, MIGRATION_STATUS_CANCELLING,

                          MIGRATION_STATUS_CANCELLED);

    }

    }



    notifier_list_notify(&migration_state_notifiers, s);

}
@@ -1028,6 +1025,7 @@ static void *migration_thread(void *opaque) 
    int64_t initial_bytes = 0;

    int64_t max_size = 0;

    int64_t start_time = initial_time;

    int64_t end_time;

    bool old_vm_running = false;



    rcu_register_thread();
@@ -1089,10 +1087,11 @@ static void *migration_thread(void *opaque) 


    /* If we enabled cpu throttling for auto-converge, turn it off. */

    cpu_throttle_stop();

    end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);



    qemu_mutex_lock_iothread();

    qemu_savevm_state_cancel();

    if (s->state == MIGRATION_STATUS_COMPLETED) {

        int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);

        uint64_t transferred_bytes = qemu_ftell(s->file);

        s->total_time = end_time - s->total_time;

        s->downtime = end_time - start_time;

migration/ram.c

+0 −1
Original line number Diff line number Diff line
@@ -1344,7 +1344,6 @@ static int ram_save_complete(QEMUFile *f, void *opaque) 


    rcu_read_unlock();



    migration_end();

    qemu_put_be64(f, RAM_SAVE_FLAG_EOS);



    return 0;