(qemu) info migrate
capabilities: xbzrle: off auto-converge: off <----
Migration status: active
total time: 1487503 milliseconds
expected downtime: 519 milliseconds
transferred ram: 383749347 kbytes
remaining ram: 2753372 kbytes
total ram: 268444224 kbytes
duplicate: 65461532 pages
skipped: 64901568 pages
normal: 95750218 pages
normal bytes: 383000872 kbytes
dirty pages rate: 67551 pages
---
(qemu) info migrate
capabilities: xbzrle: off auto-converge: on <----
Migration status: completed
total time: 241161 milliseconds
downtime: 6373 milliseconds
transferred ram: 28235307 kbytes
remaining ram: 0 kbytes
total ram: 268444224 kbytes
duplicate: 64946416 pages
skipped: 64903523 pages
normal: 7044971 pages
normal bytes: 28179884 kbytes
Signed-off-by: Chegu Vinod <address@hidden>
---
arch_init.c | 68 +++++++++++++++++++++++++++++++++++++++++
include/migration/migration.h | 4 ++
migration.c | 1 +
3 files changed, 73 insertions(+), 0 deletions(-)
diff --git a/arch_init.c b/arch_init.c
index 49c5dc2..29788d6 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -49,6 +49,7 @@
#include "trace.h"
#include "exec/cpu-all.h"
#include "hw/acpi/acpi.h"
+#include "sysemu/cpus.h"
#ifdef DEBUG_ARCH_INIT
#define DPRINTF(fmt, ...) \
@@ -104,6 +105,8 @@ int graphic_depth = 15;
#endif
const uint32_t arch_type = QEMU_ARCH;
+static bool mig_throttle_on;
+
/***********************************************************/
/* ram save/restore */
@@ -378,8 +381,15 @@ static void migration_bitmap_sync(void)
uint64_t num_dirty_pages_init = migration_dirty_pages;
MigrationState *s = migrate_get_current();
static int64_t start_time;
+ static int64_t bytes_xfer_prev;
static int64_t num_dirty_pages_period;
int64_t end_time;
+ int64_t bytes_xfer_now;
+ static int dirty_rate_high_cnt;
+
+ if (!bytes_xfer_prev) {
+ bytes_xfer_prev = ram_bytes_transferred();
+ }
if (!start_time) {
start_time = qemu_get_clock_ms(rt_clock);
@@ -404,6 +414,23 @@ static void migration_bitmap_sync(void)
/* more than 1 second = 1000 millisecons */
if (end_time > start_time + 1000) {
+ if (migrate_auto_converge()) {
+ /* The following detection logic can be refined later. For now:
+ Check to see if the dirtied bytes is 50% more than the approx.
+ amount of bytes that just got transferred since the last time we
+ were in this routine. If that happens N times (for now N==5)
+ we turn on the throttle down logic */
+ bytes_xfer_now = ram_bytes_transferred();
+ if (s->dirty_pages_rate &&
+ ((num_dirty_pages_period*TARGET_PAGE_SIZE) >
+ ((bytes_xfer_now - bytes_xfer_prev)/2))) {
+ if (dirty_rate_high_cnt++ > 5) {
+ DPRINTF("Unable to converge. Throtting down guest\n");
+ mig_throttle_on = true;
+ }
+ }
+ bytes_xfer_prev = bytes_xfer_now;
+ }
s->dirty_pages_rate = num_dirty_pages_period * 1000
/ (end_time - start_time);
s->dirty_bytes_rate = s->dirty_pages_rate * TARGET_PAGE_SIZE;
@@ -496,6 +523,15 @@ static int ram_save_block(QEMUFile *f, bool last_stage)
return bytes_sent;
}
+bool throttling_needed(void)
+{
+ if (!migrate_auto_converge()) {
+ return false;
+ }
+
+ return mig_throttle_on;
+}
+
static uint64_t bytes_transferred;
static ram_addr_t ram_save_remaining(void)
@@ -1098,3 +1134,35 @@ TargetInfo *qmp_query_target(Error **errp)
return info;
}
+
+static void mig_delay_vcpu(void)
+{
+ qemu_mutex_unlock_iothread();
+ g_usleep(50*1000);
+ qemu_mutex_lock_iothread();
+}
+
+/* Stub used for getting the vcpu out of VM and into qemu via
+ run_on_cpu()*/
+static void mig_kick_cpu(void *opq)
+{
+ mig_delay_vcpu();
+ return;
+}
+
+/* To reduce the dirty rate explicitly disallow the VCPUs from spending
+ much time in the VM. The migration thread will try to catchup.
+ Workload will experience a performance drop.
+*/
+void migration_throttle_down(void)
+{
+ if (throttling_needed()) {
+ CPUArchState *penv = first_cpu;
+ while (penv) {
+ qemu_mutex_lock_iothread();
+ async_run_on_cpu(ENV_GET_CPU(penv), mig_kick_cpu, NULL);
+ qemu_mutex_unlock_iothread();
+ penv = penv->next_cpu;
+ }
+ }
+}
diff --git a/include/migration/migration.h b/include/migration/migration.h
index ace91b0..68b65c6 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -129,4 +129,8 @@ int64_t migrate_xbzrle_cache_size(void);
int64_t xbzrle_cache_resize(int64_t new_size);
bool migrate_auto_converge(void);
+bool throttling_needed(void);
+void stop_throttling(void);
+void migration_throttle_down(void);
+
#endif
diff --git a/migration.c b/migration.c
index 570cee5..d3673a6 100644
--- a/migration.c
+++ b/migration.c
@@ -526,6 +526,7 @@ static void *migration_thread(void *opaque)
DPRINTF("pending size %lu max %lu\n", pending_size, max_size);
if (pending_size && pending_size >= max_size) {
qemu_savevm_state_iterate(s->file);
+ migration_throttle_down();
} else {
DPRINTF("done iterating\n");
qemu_mutex_lock_iothread();
--
1.7.1