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bh=i9cOhqO1L7Jwh3K0v3hi//aoSYGetnouMO5vLcBIC+k=; b=Sdcnpge4lYZ7bQoQBId3CvhQNHQm/nR25tiwpLltxp6pVfbGbLfyZ0iZzsJl0GLD4sj6xC QvFqrbapIHGFk4LpXxo9b3iGY068Gj1sYnqzFkFPc/19lTqWsMx6Tb4lHegthovC8ddRGC XRTYIO4qVCXBsd7C+pj4aAlOwWY2rY4= X-MC-Unique: QsTvdVf_PG6vkxq60n3NmQ-1 From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org Subject: [PULL 07/12] migration/colo.c: Use event instead of semaphore Date: Mon, 1 Jun 2020 19:39:59 +0100 Message-Id: <20200601184004.272784-8-dgilbert@redhat.com> In-Reply-To: <20200601184004.272784-1-dgilbert@redhat.com> References: <20200601184004.272784-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=207.211.31.120; 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charset="utf-8" From: Lukas Straub If multiple packets miscompare in a short timeframe, the semaphore value will be increased multiple times. This causes multiple checkpoints even if one would be sufficient. Fix this by using a event instead of a semaphore for triggering checkpoints. Now, checkpoint requests will be ignored until the checkpoint event is sent to colo-compare (which releases the miscompared packets). Benchmark results (iperf3): Client-to-server tcp: without patch: ~66 Mbit/s with patch: ~61 Mbit/s Server-to-client tcp: without patch: ~702 Kbit/s with patch: ~16 Mbit/s Signed-off-by: Lukas Straub Message-Id: Reviewed-by: zhanghailiang Signed-off-by: Dr. David Alan Gilbert --- migration/colo.c | 9 +++++---- migration/migration.h | 4 ++-- 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/migration/colo.c b/migration/colo.c index d015d4f84e..fe0d6e93e5 100644 --- a/migration/colo.c +++ b/migration/colo.c @@ -436,6 +436,7 @@ static int colo_do_checkpoint_transaction(MigrationStat= e *s, goto out; } =20 + qemu_event_reset(&s->colo_checkpoint_event); colo_notify_compares_event(NULL, COLO_EVENT_CHECKPOINT, &local_err); if (local_err) { goto out; @@ -589,7 +590,7 @@ static void colo_process_checkpoint(MigrationState *s) goto out; } =20 - qemu_sem_wait(&s->colo_checkpoint_sem); + qemu_event_wait(&s->colo_checkpoint_event); =20 if (s->state !=3D MIGRATION_STATUS_COLO) { goto out; @@ -637,7 +638,7 @@ out: colo_compare_unregister_notifier(&packets_compare_notifier); timer_del(s->colo_delay_timer); timer_free(s->colo_delay_timer); - qemu_sem_destroy(&s->colo_checkpoint_sem); + qemu_event_destroy(&s->colo_checkpoint_event); =20 /* * Must be called after failover BH is completed, @@ -654,7 +655,7 @@ void colo_checkpoint_notify(void *opaque) MigrationState *s =3D opaque; int64_t next_notify_time; =20 - qemu_sem_post(&s->colo_checkpoint_sem); + qemu_event_set(&s->colo_checkpoint_event); s->colo_checkpoint_time =3D qemu_clock_get_ms(QEMU_CLOCK_HOST); next_notify_time =3D s->colo_checkpoint_time + s->parameters.x_checkpoint_delay; @@ -664,7 +665,7 @@ void colo_checkpoint_notify(void *opaque) void migrate_start_colo_process(MigrationState *s) { qemu_mutex_unlock_iothread(); - qemu_sem_init(&s->colo_checkpoint_sem, 0); + qemu_event_init(&s->colo_checkpoint_event, false); s->colo_delay_timer =3D timer_new_ms(QEMU_CLOCK_HOST, colo_checkpoint_notify, s); =20 diff --git a/migration/migration.h b/migration/migration.h index 507284e563..f617960522 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -215,8 +215,8 @@ struct MigrationState /* The semaphore is used to notify COLO thread that failover is finish= ed */ QemuSemaphore colo_exit_sem; =20 - /* The semaphore is used to notify COLO thread to do checkpoint */ - QemuSemaphore colo_checkpoint_sem; + /* The event is used to notify COLO thread to do checkpoint */ + QemuEvent colo_checkpoint_event; int64_t colo_checkpoint_time; QEMUTimer *colo_delay_timer; =20 --=20 2.26.2