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Re: [Qemu-devel] [RFC 18/29] migration: new state "postcopy-recover"
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC 18/29] migration: new state "postcopy-recover" |
Date: |
Tue, 1 Aug 2017 12:36:22 +0100 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
* Peter Xu (address@hidden) wrote:
> Introducing new migration state "postcopy-recover". If a migration
> procedure is paused and the connection is rebuilt afterward
> successfully, we'll switch the source VM state from "postcopy-paused" to
> the new state "postcopy-recover", then we'll do the resume logic in the
> migration thread (along with the return path thread).
>
> This patch only do the state switch on source side. Another following up
> patch will handle the state switching on destination side using the same
> status bit.
>
> Signed-off-by: Peter Xu <address@hidden>
> ---
> migration/migration.c | 45 +++++++++++++++++++++++++++++++++++++++++----
> qapi-schema.json | 4 +++-
> 2 files changed, 44 insertions(+), 5 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 64de0ee..3aabe11 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -495,6 +495,7 @@ static bool migration_is_setup_or_active(int state)
> case MIGRATION_STATUS_ACTIVE:
> case MIGRATION_STATUS_POSTCOPY_ACTIVE:
> case MIGRATION_STATUS_POSTCOPY_PAUSED:
> + case MIGRATION_STATUS_POSTCOPY_RECOVER:
> case MIGRATION_STATUS_SETUP:
> return true;
>
> @@ -571,6 +572,7 @@ MigrationInfo *qmp_query_migrate(Error **errp)
> case MIGRATION_STATUS_CANCELLING:
> case MIGRATION_STATUS_POSTCOPY_ACTIVE:
> case MIGRATION_STATUS_POSTCOPY_PAUSED:
> + case MIGRATION_STATUS_POSTCOPY_RECOVER:
> /* TODO add some postcopy stats */
> info->has_status = true;
> info->has_total_time = true;
> @@ -2018,6 +2020,13 @@ static bool postcopy_should_start(MigrationState *s)
> return atomic_read(&s->start_postcopy) || s->start_postcopy_fast;
> }
>
> +/* Return zero if success, or <0 for error */
> +static int postcopy_do_resume(MigrationState *s)
> +{
> + /* TODO: do the resume logic */
> + return 0;
> +}
> +
> /*
> * We don't return until we are in a safe state to continue current
> * postcopy migration. Returns true to continue the migration, or
> @@ -2026,7 +2035,9 @@ static bool postcopy_should_start(MigrationState *s)
> static bool postcopy_pause(MigrationState *s)
> {
> assert(s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
> - migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
> +
> +do_pause:
> + migrate_set_state(&s->state, s->state,
> MIGRATION_STATUS_POSTCOPY_PAUSED);
>
> /* Current channel is possibly broken. Release it. */
> @@ -2043,9 +2054,32 @@ static bool postcopy_pause(MigrationState *s)
> qemu_sem_wait(&s->postcopy_pause_sem);
> }
>
> - trace_postcopy_pause_continued();
> + if (s->state == MIGRATION_STATUS_POSTCOPY_RECOVER) {
> + /* We were waken up by a recover procedure. Give it a shot */
>
> - return true;
> + /*
> + * Firstly, let's wake up the return path now, with a new
> + * return path channel.
> + */
> + qemu_sem_post(&s->postcopy_pause_rp_sem);
> +
> + /* Do the resume logic */
> + if (postcopy_do_resume(s) == 0) {
> + /* Let's continue! */
> + trace_postcopy_pause_continued();
> + return true;
> + } else {
> + /*
> + * Something wrong happened during the recovery, let's
> + * pause again. Pause is always better than throwing data
> + * away.
> + */
> + goto do_pause;
You should be able to turn this around into a do {} while or similar
rather than goto.
Dave
> + }
> + } else {
> + /* This is not right... Time to quit. */
> + return false;
> + }
> }
>
> /* Return true if we want to stop the migration, otherwise false. */
> @@ -2300,7 +2334,10 @@ void migrate_fd_connect(MigrationState *s)
> }
>
> if (resume) {
> - /* TODO: do the resume logic */
> + /* Wakeup the main migration thread to do the recovery */
> + migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_PAUSED,
> + MIGRATION_STATUS_POSTCOPY_RECOVER);
> + qemu_sem_post(&s->postcopy_pause_sem);
> return;
> }
>
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 27b7c4c..10f1f60 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -669,6 +669,8 @@
> #
> # @postcopy-paused: during postcopy but paused. (since 2.10)
> #
> +# @postcopy-recover: trying to recover from a paused postcopy. (since 2.11)
> +#
> # @completed: migration is finished.
> #
> # @failed: some error occurred during migration process.
> @@ -682,7 +684,7 @@
> { 'enum': 'MigrationStatus',
> 'data': [ 'none', 'setup', 'cancelling', 'cancelled',
> 'active', 'postcopy-active', 'postcopy-paused',
> - 'completed', 'failed', 'colo' ] }
> + 'postcopy-recover', 'completed', 'failed', 'colo' ] }
>
> ##
> # @MigrationInfo:
> --
> 2.7.4
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- Re: [Qemu-devel] [RFC 18/29] migration: new state "postcopy-recover",
Dr. David Alan Gilbert <=