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Wed, 19 Feb 2020 18:51:20 +0000 (UTC) Date: Wed, 19 Feb 2020 18:51:17 +0000 From: "Dr. David Alan Gilbert" To: Hailiang Zhang Subject: Re: [PATCH 2/3] COLO: Migrate dirty pages during the gap of checkpointing Message-ID: <20200219185117.GJ3089@work-vm> References: <20200217012049.22988-1-zhang.zhanghailiang@huawei.com> <20200217012049.22988-3-zhang.zhanghailiang@huawei.com> MIME-Version: 1.0 In-Reply-To: <20200217012049.22988-3-zhang.zhanghailiang@huawei.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: Kn8hNWH4PQyFXpWic577Hg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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: danielcho@qnap.com, chen.zhang@intel.com, qemu-devel@nongnu.org, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Hailiang Zhang (zhang.zhanghailiang@huawei.com) wrote: > We can migrate some dirty pages during the gap of checkpointing, > by this way, we can reduce the amount of ram migrated during checkpointin= g. >=20 > Signed-off-by: Hailiang Zhang > --- > migration/colo.c | 69 +++++++++++++++++++++++++++++++++++++++--- > migration/migration.h | 1 + > migration/trace-events | 1 + > qapi/migration.json | 4 ++- > 4 files changed, 70 insertions(+), 5 deletions(-) >=20 > diff --git a/migration/colo.c b/migration/colo.c > index 93c5a452fb..d30c6bc4ad 100644 > --- a/migration/colo.c > +++ b/migration/colo.c > @@ -46,6 +46,13 @@ static COLOMode last_colo_mode; > =20 > #define COLO_BUFFER_BASE_SIZE (4 * 1024 * 1024) > =20 > +#define DEFAULT_RAM_PENDING_CHECK 1000 > + > +/* should be calculated by bandwidth and max downtime ? */ > +#define THRESHOLD_PENDING_SIZE (100 * 1024 * 1024UL) Turn both of these magic constants into parameters. > +static int checkpoint_request; > + > bool migration_in_colo_state(void) > { > MigrationState *s =3D migrate_get_current(); > @@ -516,6 +523,20 @@ static void colo_compare_notify_checkpoint(Notifier = *notifier, void *data) > colo_checkpoint_notify(data); > } > =20 > +static bool colo_need_migrate_ram_background(MigrationState *s) > +{ > + uint64_t pending_size, pend_pre, pend_compat, pend_post; > + int64_t max_size =3D THRESHOLD_PENDING_SIZE; > + > + qemu_savevm_state_pending(s->to_dst_file, max_size, &pend_pre, > + &pend_compat, &pend_post); > + pending_size =3D pend_pre + pend_compat + pend_post; > + > + trace_colo_need_migrate_ram_background(pending_size); > + return (pending_size >=3D max_size); > +} > + > + > static void colo_process_checkpoint(MigrationState *s) > { > QIOChannelBuffer *bioc; > @@ -571,6 +592,8 @@ static void colo_process_checkpoint(MigrationState *s= ) > =20 > 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); What happens if the iterate takes a while and this triggers in the middle of the iterate? > while (s->state =3D=3D MIGRATION_STATUS_COLO) { > if (failover_get_state() !=3D FAILOVER_STATUS_NONE) { > @@ -583,10 +606,25 @@ static void colo_process_checkpoint(MigrationState = *s) > if (s->state !=3D MIGRATION_STATUS_COLO) { > goto out; > } > - ret =3D colo_do_checkpoint_transaction(s, bioc, fb); > - if (ret < 0) { > - goto out; > - } > + if (atomic_xchg(&checkpoint_request, 0)) { > + /* start a colo checkpoint */ > + ret =3D 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); Maybe you should do a qemu_file_get_error(..) at this point to check it's OK. > + } > + } > } > =20 > out: > @@ -626,6 +664,8 @@ 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); > =20 > /* > @@ -643,6 +683,7 @@ void colo_checkpoint_notify(void *opaque) > MigrationState *s =3D opaque; > int64_t next_notify_time; > =20 > + atomic_inc(&checkpoint_request); Can you explain what you've changed about this atomic in this patch, I don't quite see what you're doing. > qemu_sem_post(&s->colo_checkpoint_sem); > s->colo_checkpoint_time =3D qemu_clock_get_ms(QEMU_CLOCK_HOST); > next_notify_time =3D s->colo_checkpoint_time + > @@ -650,6 +691,19 @@ void colo_checkpoint_notify(void *opaque) > timer_mod(s->colo_delay_timer, next_notify_time); > } > =20 > +static void colo_pending_ram_check_notify(void *opaque) > +{ > + int64_t next_notify_time; > + MigrationState *s =3D opaque; > + > + if (migration_in_colo_state()) { > + next_notify_time =3D 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(); > @@ -657,6 +711,8 @@ void migrate_start_colo_process(MigrationState *s) > s->colo_delay_timer =3D timer_new_ms(QEMU_CLOCK_HOST, > colo_checkpoint_notify, s); > =20 > + s->pending_ram_check_timer =3D 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); > @@ -805,6 +861,11 @@ static void colo_wait_handle_message(MigrationIncomi= ngState *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"); > + } OK, that's a little dangerou, in that it relies on the source being good and only sending iterative data; stuff would break badly if it actually sent you devices. > + 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; > =20 > /* 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' =3D>= '%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%" PR= Ix64 " dirty ram" > =20 > # 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 b7348d0c8b..ff7a4f18b0 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' ] } > =20 > ## > # @COLOMode: > --=20 > 2.21.0 >=20 >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK