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Re: [Qemu-devel] [PATCH v4 05/32] migration: implement "postcopy-pause"
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v4 05/32] migration: implement "postcopy-pause" src logic |
Date: |
Thu, 30 Nov 2017 10:49:45 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
* Peter Xu (address@hidden) wrote:
> Now when network down for postcopy, the source side will not fail the
> migration. Instead we convert the status into this new paused state, and
> we will try to wait for a rescue in the future.
>
> If a recovery is detected, migration_thread() will reset its local
> variables to prepare for that.
>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
That's still OK; you might want to consider reusing the 'pause_sem' that I
added to MigrationStatus for the other pause case.
Dave
> Signed-off-by: Peter Xu <address@hidden>
> ---
> migration/migration.c | 98
> +++++++++++++++++++++++++++++++++++++++++++++++---
> migration/migration.h | 3 ++
> migration/trace-events | 1 +
> 3 files changed, 98 insertions(+), 4 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index dd270f8bc5..46e7ca36a4 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1111,6 +1111,8 @@ static void migrate_fd_cleanup(void *opaque)
> }
> notifier_list_notify(&migration_state_notifiers, s);
> block_cleanup_parameters(s);
> +
> + qemu_sem_destroy(&s->postcopy_pause_sem);
> }
>
> void migrate_set_error(MigrationState *s, const Error *error)
> @@ -1267,6 +1269,7 @@ MigrationState *migrate_init(void)
> s->migration_thread_running = false;
> error_free(s->error);
> s->error = NULL;
> + qemu_sem_init(&s->postcopy_pause_sem, 0);
>
> migrate_set_state(&s->state, MIGRATION_STATUS_NONE,
> MIGRATION_STATUS_SETUP);
>
> @@ -2159,6 +2162,80 @@ bool migrate_colo_enabled(void)
> return s->enabled_capabilities[MIGRATION_CAPABILITY_X_COLO];
> }
>
> +typedef enum MigThrError {
> + /* No error detected */
> + MIG_THR_ERR_NONE = 0,
> + /* Detected error, but resumed successfully */
> + MIG_THR_ERR_RECOVERED = 1,
> + /* Detected fatal error, need to exit */
> + MIG_THR_ERR_FATAL = 2,
> +} MigThrError;
> +
> +/*
> + * We don't return until we are in a safe state to continue current
> + * postcopy migration. Returns MIG_THR_ERR_RECOVERED if recovered, or
> + * MIG_THR_ERR_FATAL if unrecovery failure happened.
> + */
> +static MigThrError postcopy_pause(MigrationState *s)
> +{
> + assert(s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
> + migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
> + MIGRATION_STATUS_POSTCOPY_PAUSED);
> +
> + /* Current channel is possibly broken. Release it. */
> + assert(s->to_dst_file);
> + qemu_file_shutdown(s->to_dst_file);
> + qemu_fclose(s->to_dst_file);
> + s->to_dst_file = NULL;
> +
> + error_report("Detected IO failure for postcopy. "
> + "Migration paused.");
> +
> + /*
> + * We wait until things fixed up. Then someone will setup the
> + * status back for us.
> + */
> + while (s->state == MIGRATION_STATUS_POSTCOPY_PAUSED) {
> + qemu_sem_wait(&s->postcopy_pause_sem);
> + }
> +
> + trace_postcopy_pause_continued();
> +
> + return MIG_THR_ERR_RECOVERED;
> +}
> +
> +static MigThrError migration_detect_error(MigrationState *s)
> +{
> + int ret;
> +
> + /* Try to detect any file errors */
> + ret = qemu_file_get_error(s->to_dst_file);
> +
> + if (!ret) {
> + /* Everything is fine */
> + return MIG_THR_ERR_NONE;
> + }
> +
> + if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE && ret == -EIO) {
> + /*
> + * For postcopy, we allow the network to be down for a
> + * while. After that, it can be continued by a
> + * recovery phase.
> + */
> + return postcopy_pause(s);
> + } else {
> + /*
> + * For precopy (or postcopy with error outside IO), we fail
> + * with no time.
> + */
> + migrate_set_state(&s->state, s->state, MIGRATION_STATUS_FAILED);
> + trace_migration_thread_file_err();
> +
> + /* Time to stop the migration, now. */
> + return MIG_THR_ERR_FATAL;
> + }
> +}
> +
> /*
> * Master migration thread on the source VM.
> * It drives the migration and pumps the data down the outgoing channel.
> @@ -2183,6 +2260,7 @@ static void *migration_thread(void *opaque)
> /* The active state we expect to be in; ACTIVE or POSTCOPY_ACTIVE */
> enum MigrationStatus current_active_state = MIGRATION_STATUS_ACTIVE;
> bool enable_colo = migrate_colo_enabled();
> + MigThrError thr_error;
>
> rcu_register_thread();
>
> @@ -2255,12 +2333,24 @@ static void *migration_thread(void *opaque)
> }
> }
>
> - if (qemu_file_get_error(s->to_dst_file)) {
> - migrate_set_state(&s->state, current_active_state,
> - MIGRATION_STATUS_FAILED);
> - trace_migration_thread_file_err();
> + /*
> + * Try to detect any kind of failures, and see whether we
> + * should stop the migration now.
> + */
> + thr_error = migration_detect_error(s);
> + if (thr_error == MIG_THR_ERR_FATAL) {
> + /* Stop migration */
> break;
> + } else if (thr_error == MIG_THR_ERR_RECOVERED) {
> + /*
> + * Just recovered from a e.g. network failure, reset all
> + * the local variables. This is important to avoid
> + * breaking transferred_bytes and bandwidth calculation
> + */
> + initial_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
> + initial_bytes = 0;
> }
> +
> current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
> if (current_time >= initial_time + BUFFER_DELAY) {
> uint64_t transferred_bytes = qemu_ftell(s->to_dst_file) -
> diff --git a/migration/migration.h b/migration/migration.h
> index 6d36400975..36aaa13f50 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -156,6 +156,9 @@ struct MigrationState
> bool send_configuration;
> /* Whether we send section footer during migration */
> bool send_section_footer;
> +
> + /* Needed by postcopy-pause state */
> + QemuSemaphore postcopy_pause_sem;
> };
>
> void migrate_set_state(int *state, int old_state, int new_state);
> diff --git a/migration/trace-events b/migration/trace-events
> index 6f29fcc686..da1c63a933 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -99,6 +99,7 @@ migration_thread_setup_complete(void) ""
> open_return_path_on_source(void) ""
> open_return_path_on_source_continue(void) ""
> postcopy_start(void) ""
> +postcopy_pause_continued(void) ""
> postcopy_start_set_run(void) ""
> source_return_path_thread_bad_end(void) ""
> source_return_path_thread_end(void) ""
> --
> 2.13.6
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH v4 26/32] migration: return incoming task tag for fd, (continued)
- [Qemu-devel] [PATCH v4 26/32] migration: return incoming task tag for fd, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 27/32] migration: store listen task tag, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 29/32] migration: init dst in migration_object_init too, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 30/32] migration: delay the postcopy-active state switch, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 32/32] migration, hmp: new command "migrate_pause", Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 31/32] migration, qmp: new command "migrate-pause", Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 24/32] migration: return incoming task tag for sockets, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 25/32] migration: return incoming task tag for exec, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 14/32] migration: wakeup dst ram-load-thread for recover, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 05/32] migration: implement "postcopy-pause" src logic, Peter Xu, 2017/11/08
- Re: [Qemu-devel] [PATCH v4 05/32] migration: implement "postcopy-pause" src logic,
Dr. David Alan Gilbert <=
- [Qemu-devel] [PATCH v4 07/32] migration: allow src return path to pause, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 12/32] migration: rebuild channel on source, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 13/32] migration: new state "postcopy-recover", Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 16/32] migration: new message MIG_RP_MSG_RECV_BITMAP, Peter Xu, 2017/11/08
- [Qemu-devel] [PATCH v4 28/32] migration: allow migrate_incoming for paused VM, Peter Xu, 2017/11/08