[RFC,3/6] migration: Implement dirtylimit convergence algo

Commit Message

Hyman Huang May 17, 2022, 6:35 a.m. UTC

From: Hyman Huang(黄勇) <[e-mail]>

Implement dirtylimit convergence algo for live migration,
which is kind of like auto-converge algo but using dirtylimit
instead of cpu throttle to make migration convergent.

Signed-off-by: Hyman Huang(黄勇) <[e-mail]>
---
 migration/ram.c        | 53 +++++++++++++++++++++++++++++++++++++-------------
 migration/trace-events |  1 +
 2 files changed, 41 insertions(+), 13 deletions(-)

Patch

diff --git a/migration/ram.c b/migration/ram.c
index 3532f64..5dd3e69 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -44,6 +44,7 @@ 
 #include "qapi/error.h"
 #include "qapi/qapi-types-migration.h"
 #include "qapi/qapi-events-migration.h"
+#include "qapi/qapi-commands-migration.h"
 #include "qapi/qmp/qerror.h"
 #include "trace.h"
 #include "exec/ram_addr.h"
@@ -56,6 +57,8 @@ 
 #include "qemu/iov.h"
 #include "multifd.h"
 #include "sysemu/runstate.h"
+#include "sysemu/dirtylimit.h"
+#include "sysemu/kvm.h"
 
 #include "hw/boards.h" /* for machine_dump_guest_core() */
 
@@ -1082,6 +1085,21 @@  static void migration_update_rates(RAMState *rs, int64_t end_time)
     }
 }
 
+/*
+ * Enable dirtylimit to throttle down the guest
+ */
+static void migration_dirtylimit_guest(void)
+{
+    if (!dirtylimit_in_service()) {
+        MigrationState *s = migrate_get_current();
+        int64_t quota_dirtyrate = s->parameters.vcpu_dirtylimit;
+
+        /* Set quota dirtyrate if dirty limit not in service */
+        qmp_set_vcpu_dirty_limit(false, -1, quota_dirtyrate, NULL);
+        trace_migration_dirtylimit_guest(quota_dirtyrate);
+    }
+}
+
 static void migration_trigger_throttle(RAMState *rs)
 {
     MigrationState *s = migrate_get_current();
@@ -1091,22 +1109,31 @@  static void migration_trigger_throttle(RAMState *rs)
     uint64_t bytes_dirty_period = rs->num_dirty_pages_period * TARGET_PAGE_SIZE;
     uint64_t bytes_dirty_threshold = bytes_xfer_period * threshold / 100;
 
-    /* During block migration the auto-converge logic incorrectly detects
-     * that ram migration makes no progress. Avoid this by disabling the
-     * throttling logic during the bulk phase of block migration. */
-    if (migrate_auto_converge() && !blk_mig_bulk_active()) {
-        /* The following detection logic can be refined later. For now:
-           Check to see if the ratio between dirtied bytes and the approx.
-           amount of bytes that just got transferred since the last time
-           we were in this routine reaches the threshold. If that happens
-           twice, start or increase throttling. */
-
-        if ((bytes_dirty_period > bytes_dirty_threshold) &&
-            (++rs->dirty_rate_high_cnt >= 2)) {
+    /*
+     * The following detection logic can be refined later. For now:
+     * Check to see if the ratio between dirtied bytes and the approx.
+     * amount of bytes that just got transferred since the last time
+     * we were in this routine reaches the threshold. If that happens
+     * twice, start or increase throttling.
+     */
+
+    if ((bytes_dirty_period > bytes_dirty_threshold) &&
+        (++rs->dirty_rate_high_cnt >= 2)) {
+        rs->dirty_rate_high_cnt = 0;
+        /*
+         * During block migration the auto-converge logic incorrectly detects
+         * that ram migration makes no progress. Avoid this by disabling the
+         * throttling logic during the bulk phase of block migration.
+         */
+
+        if (migrate_auto_converge() && !blk_mig_bulk_active()) {
             trace_migration_throttle();
-            rs->dirty_rate_high_cnt = 0;
             mig_throttle_guest_down(bytes_dirty_period,
                                     bytes_dirty_threshold);
+        } else if (migrate_dirtylimit() &&
+                   kvm_dirty_ring_enabled() &&
+                   migration_is_active(s)) {
+            migration_dirtylimit_guest();
         }
     }
 }
diff --git a/migration/trace-events b/migration/trace-events
index 1aec580..2c341fc 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -89,6 +89,7 @@  migration_bitmap_sync_start(void) ""
 migration_bitmap_sync_end(uint64_t dirty_pages) "dirty_pages %" PRIu64
 migration_bitmap_clear_dirty(char *str, uint64_t start, uint64_t size, unsigned long page) "rb %s start 0x%"PRIx64" size 0x%"PRIx64" page 0x%lx"
 migration_throttle(void) ""
+migration_dirtylimit_guest(int64_t dirtyrate) "guest dirty page rate limit %" PRIi64 " MB/s"
 ram_discard_range(const char *rbname, uint64_t start, size_t len) "%s: start: %" PRIx64 " %zx"
 ram_load_loop(const char *rbname, uint64_t addr, int flags, void *host) "%s: addr: 0x%" PRIx64 " flags: 0x%x host: %p"
 ram_load_postcopy_loop(uint64_t addr, int flags) "@%" PRIx64 " %x"