[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH] migration: always initial ram_counters for a new mi
From: |
Ivan Ren |
Subject: |
[Qemu-devel] [PATCH] migration: always initial ram_counters for a new migration |
Date: |
Tue, 30 Jul 2019 13:36:32 +0800 |
From: Ivan Ren <address@hidden>
This patch fix a multifd migration bug in migration speed calculation, this
problem can be reproduced as follows:
1. start a vm and give a heavy memory write stress to prevent the vm be
successfully migrated to destination
2. begin a migration with multifd
3. migrate for a long time [actually, this can be measured by transferred bytes]
4. migrate cancel
5. begin a new migration with multifd, the migration will directly run into
migration_completion phase
Reason as follows:
Migration update bandwidth and s->threshold_size in function
migration_update_counters after BUFFER_DELAY time:
current_bytes = migration_total_bytes(s);
transferred = current_bytes - s->iteration_initial_bytes;
time_spent = current_time - s->iteration_start_time;
bandwidth = (double)transferred / time_spent;
s->threshold_size = bandwidth * s->parameters.downtime_limit;
In multifd migration, migration_total_bytes function return
qemu_ftell(s->to_dst_file) + ram_counters.multifd_bytes.
s->iteration_initial_bytes will be initialized to 0 at every new migration,
but ram_counters is a global variable, and history migration data will be
accumulated. So if the ram_counters.multifd_bytes is big enough, it may lead
pending_size >= s->threshold_size become false in migration_iteration_run
after the first migration_update_counters.
Signed-off-by: Ivan Ren <address@hidden>
---
migration/migration.c | 15 ++++++++++++++-
migration/savevm.c | 1 +
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/migration/migration.c b/migration/migration.c
index 8a607fe1e2..d35a6ae6f9 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1908,6 +1908,11 @@ static bool migrate_prepare(MigrationState *s, bool blk,
bool blk_inc,
}
migrate_init(s);
+ /*
+ * set ram_counters memory to zero for a
+ * new migration
+ */
+ memset(&ram_counters, 0, sizeof(ram_counters));
return true;
}
@@ -3187,6 +3192,10 @@ static void *migration_thread(void *opaque)
object_ref(OBJECT(s));
s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+ /*
+ * Update s->iteration_initial_bytes to match s->iteration_start_time.
+ */
+ s->iteration_initial_bytes = migration_total_bytes(s);
qemu_savevm_state_header(s->to_dst_file);
@@ -3252,7 +3261,11 @@ static void *migration_thread(void *opaque)
* breaking transferred_bytes and bandwidth calculation
*/
s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
- s->iteration_initial_bytes = 0;
+ /*
+ * Update s->iteration_initial_bytes to current size to
+ * avoid historical data lead wrong bandwidth.
+ */
+ s->iteration_initial_bytes = migration_total_bytes(s);
}
current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
diff --git a/migration/savevm.c b/migration/savevm.c
index 79ed44d475..480c511b19 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1424,6 +1424,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
}
migrate_init(ms);
+ memset(&ram_counters, 0, sizeof(ram_counters));
ms->to_dst_file = f;
qemu_mutex_unlock_iothread();
--
2.17.2 (Apple Git-113)
- [Qemu-devel] [PATCH] migration: always initial ram_counters for a new migration,
Ivan Ren <=