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Re: [PATCH V2 7/8] COLO: Migrate dirty pages during the gap of checkpoin
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH V2 7/8] COLO: Migrate dirty pages during the gap of checkpointing |
Date: |
Thu, 12 Mar 2020 19:50:52 +0000 |
User-agent: |
Mutt/1.13.3 (2020-01-12) |
* zhanghailiang (address@hidden) wrote:
> We can migrate some dirty pages during the gap of checkpointing,
> by this way, we can reduce the amount of ram migrated during checkpointing.
>
> Signed-off-by: zhanghailiang <address@hidden>
> ---
> migration/colo.c | 73 ++++++++++++++++++++++++++++++++++++++++--
> migration/migration.h | 1 +
> migration/trace-events | 1 +
> qapi/migration.json | 4 ++-
> 4 files changed, 75 insertions(+), 4 deletions(-)
>
> diff --git a/migration/colo.c b/migration/colo.c
> index 44942c4e23..c36d94072f 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -47,6 +47,13 @@ static COLOMode last_colo_mode;
>
> #define COLO_BUFFER_BASE_SIZE (4 * 1024 * 1024)
>
> +#define DEFAULT_RAM_PENDING_CHECK 1000
> +
> +/* should be calculated by bandwidth and max downtime ? */
> +#define THRESHOLD_PENDING_SIZE (100 * 1024 * 1024UL)
In the last version I asked to change these two values to parameters.
Dave
> +static int checkpoint_request;
> +
> bool migration_in_colo_state(void)
> {
> MigrationState *s = migrate_get_current();
> @@ -517,6 +524,20 @@ static void colo_compare_notify_checkpoint(Notifier
> *notifier, void *data)
> colo_checkpoint_notify(data);
> }
>
> +static bool colo_need_migrate_ram_background(MigrationState *s)
> +{
> + uint64_t pending_size, pend_pre, pend_compat, pend_post;
> + int64_t max_size = THRESHOLD_PENDING_SIZE;
> +
> + qemu_savevm_state_pending(s->to_dst_file, max_size, &pend_pre,
> + &pend_compat, &pend_post);
> + pending_size = pend_pre + pend_compat + pend_post;
> +
> + trace_colo_need_migrate_ram_background(pending_size);
> + return (pending_size >= max_size);
> +}
> +
> +
> static void colo_process_checkpoint(MigrationState *s)
> {
> QIOChannelBuffer *bioc;
> @@ -572,6 +593,8 @@ static void colo_process_checkpoint(MigrationState *s)
>
> timer_mod(s->colo_delay_timer,
> current_time + s->parameters.x_checkpoint_delay);
> + timer_mod(s->pending_ram_check_timer,
> + current_time + DEFAULT_RAM_PENDING_CHECK);
>
> while (s->state == MIGRATION_STATUS_COLO) {
> if (failover_get_state() != FAILOVER_STATUS_NONE) {
> @@ -584,9 +607,30 @@ static void colo_process_checkpoint(MigrationState *s)
> if (s->state != MIGRATION_STATUS_COLO) {
> goto out;
> }
> - ret = colo_do_checkpoint_transaction(s, bioc, fb);
> - if (ret < 0) {
> - goto out;
> + if (atomic_xchg(&checkpoint_request, 0)) {
> + /* start a colo checkpoint */
> + ret = colo_do_checkpoint_transaction(s, bioc, fb);
> + if (ret < 0) {
> + goto out;
> + }
> + } else {
> + if (colo_need_migrate_ram_background(s)) {
> + colo_send_message(s->to_dst_file,
> + COLO_MESSAGE_MIGRATE_RAM_BACKGROUND,
> + &local_err);
> + if (local_err) {
> + goto out;
> + }
> +
> + qemu_savevm_state_iterate(s->to_dst_file, false);
> + qemu_put_byte(s->to_dst_file, QEMU_VM_EOF);
> + ret = qemu_file_get_error(s->to_dst_file);
> + if (ret < 0) {
> + error_setg_errno(&local_err, -ret,
> + "Failed to send dirty pages backgroud");
> + goto out;
> + }
> + }
> }
> }
>
> @@ -627,6 +671,8 @@ out:
> colo_compare_unregister_notifier(&packets_compare_notifier);
> timer_del(s->colo_delay_timer);
> timer_free(s->colo_delay_timer);
> + timer_del(s->pending_ram_check_timer);
> + timer_free(s->pending_ram_check_timer);
> qemu_sem_destroy(&s->colo_checkpoint_sem);
>
> /*
> @@ -644,6 +690,7 @@ void colo_checkpoint_notify(void *opaque)
> MigrationState *s = opaque;
> int64_t next_notify_time;
>
> + atomic_inc(&checkpoint_request);
> qemu_sem_post(&s->colo_checkpoint_sem);
> s->colo_checkpoint_time = qemu_clock_get_ms(QEMU_CLOCK_HOST);
> next_notify_time = s->colo_checkpoint_time +
> @@ -651,6 +698,19 @@ void colo_checkpoint_notify(void *opaque)
> timer_mod(s->colo_delay_timer, next_notify_time);
> }
>
> +static void colo_pending_ram_check_notify(void *opaque)
> +{
> + int64_t next_notify_time;
> + MigrationState *s = opaque;
> +
> + if (migration_in_colo_state()) {
> + next_notify_time = DEFAULT_RAM_PENDING_CHECK +
> + qemu_clock_get_ms(QEMU_CLOCK_HOST);
> + timer_mod(s->pending_ram_check_timer, next_notify_time);
> + qemu_sem_post(&s->colo_checkpoint_sem);
> + }
> +}
> +
> void migrate_start_colo_process(MigrationState *s)
> {
> qemu_mutex_unlock_iothread();
> @@ -658,6 +718,8 @@ void migrate_start_colo_process(MigrationState *s)
> s->colo_delay_timer = timer_new_ms(QEMU_CLOCK_HOST,
> colo_checkpoint_notify, s);
>
> + s->pending_ram_check_timer = timer_new_ms(QEMU_CLOCK_HOST,
> + colo_pending_ram_check_notify, s);
> qemu_sem_init(&s->colo_exit_sem, 0);
> migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
> MIGRATION_STATUS_COLO);
> @@ -806,6 +868,11 @@ static void
> colo_wait_handle_message(MigrationIncomingState *mis,
> case COLO_MESSAGE_CHECKPOINT_REQUEST:
> colo_incoming_process_checkpoint(mis, fb, bioc, errp);
> break;
> + case COLO_MESSAGE_MIGRATE_RAM_BACKGROUND:
> + if (qemu_loadvm_state_main(mis->from_src_file, mis) < 0) {
> + error_setg(errp, "Load ram background failed");
> + }
> + break;
> default:
> error_setg(errp, "Got unknown COLO message: %d", msg);
> break;
> diff --git a/migration/migration.h b/migration/migration.h
> index 8473ddfc88..5355259789 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -219,6 +219,7 @@ struct MigrationState
> QemuSemaphore colo_checkpoint_sem;
> int64_t colo_checkpoint_time;
> QEMUTimer *colo_delay_timer;
> + QEMUTimer *pending_ram_check_timer;
>
> /* The first error that has occurred.
> We used the mutex to be able to return the 1st error message */
> diff --git a/migration/trace-events b/migration/trace-events
> index 4ab0a503d2..f2ed0c8645 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -295,6 +295,7 @@ migration_tls_incoming_handshake_complete(void) ""
> colo_vm_state_change(const char *old, const char *new) "Change '%s' => '%s'"
> colo_send_message(const char *msg) "Send '%s' message"
> colo_receive_message(const char *msg) "Receive '%s' message"
> +colo_need_migrate_ram_background(uint64_t pending_size) "Pending 0x%" PRIx64
> " dirty ram"
>
> # colo-failover.c
> colo_failover_set_state(const char *new_state) "new state %s"
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 52f3429969..73445f1978 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -977,12 +977,14 @@
> #
> # @vmstate-loaded: VM's state has been loaded by SVM.
> #
> +# @migrate-ram-background: Send some dirty pages during the gap of COLO
> checkpoint
> +#
> # Since: 2.8
> ##
> { 'enum': 'COLOMessage',
> 'data': [ 'checkpoint-ready', 'checkpoint-request', 'checkpoint-reply',
> 'vmstate-send', 'vmstate-size', 'vmstate-received',
> - 'vmstate-loaded' ] }
> + 'vmstate-loaded', 'migrate-ram-background' ] }
>
> ##
> # @COLOMode:
> --
> 2.21.0
>
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
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