[PATCH v1 3/8] migration: Introduce dirty-limit capability

[huangy81@chinatelecom.cn]

From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>

Introduce migration dirty-limit capability, which can
be turned on before live migration and limit dirty
page rate durty live migration.

Introduce migrate_dirty_limit function to help check
if dirty-limit capability enabled during live migration.

Meanwhile, refactor vcpu_dirty_rate_stat_collect
so that period can be configured instead of hardcoded.

dirty-limit capability is kind of like auto-converge
but using dirty limit instead of traditional cpu-throttle
to throttle guest down. To enable this feature, turn on
the dirty-limit capability before live migration using
migratioin-set-capabilities, and set the parameters
"x-vcpu-dirty-limit-period", "vcpu-dirty-limit" suitably
to speed up convergence.

Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
---
 migration/migration.c | 10 ++++++++++
 migration/migration.h |  1 +
 qapi/migration.json   |  4 +++-
 softmmu/dirtylimit.c  | 11 ++++++++++-
 4 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index a748fe5..d117bb4 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2508,6 +2508,15 @@ bool migrate_auto_converge(void)
     return s->enabled_capabilities[MIGRATION_CAPABILITY_AUTO_CONVERGE];
 }
 
+bool migrate_dirty_limit(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_DIRTY_LIMIT];
+}
+
 bool migrate_zero_blocks(void)
 {
     MigrationState *s;
@@ -4437,6 +4446,7 @@ static Property migration_properties[] = {
     DEFINE_PROP_MIG_CAP("x-zero-copy-send",
             MIGRATION_CAPABILITY_ZERO_COPY_SEND),
 #endif
+    DEFINE_PROP_MIG_CAP("x-dirty-limit", MIGRATION_CAPABILITY_DIRTY_LIMIT),
 
     DEFINE_PROP_END_OF_LIST(),
 };
diff --git a/migration/migration.h b/migration/migration.h
index cdad8ac..7fbb9f8 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -409,6 +409,7 @@ bool migrate_ignore_shared(void);
 bool migrate_validate_uuid(void);
 
 bool migrate_auto_converge(void);
+bool migrate_dirty_limit(void);
 bool migrate_use_multifd(void);
 bool migrate_pause_before_switchover(void);
 int migrate_multifd_channels(void);
diff --git a/qapi/migration.json b/qapi/migration.json
index 8554d33..bc4bc96 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -477,6 +477,8 @@
 #                    will be handled faster.  This is a performance feature and
 #                    should not affect the correctness of postcopy migration.
 #                    (since 7.1)
+# @dirty-limit: Use dirty-limit to throttle down guest if enabled.
+#               (since 7.1)
 #
 # Features:
 # @unstable: Members @x-colo and @x-ignore-shared are experimental.
@@ -492,7 +494,7 @@
            'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
            { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
            'validate-uuid', 'background-snapshot',
-           'zero-copy-send', 'postcopy-preempt'] }
+           'zero-copy-send', 'postcopy-preempt', 'dirty-limit'] }
 
 ##
 # @MigrationCapabilityStatus:
diff --git a/softmmu/dirtylimit.c b/softmmu/dirtylimit.c
index 8d98cb7..1fdd8c6 100644
--- a/softmmu/dirtylimit.c
+++ b/softmmu/dirtylimit.c
@@ -23,6 +23,8 @@
 #include "exec/memory.h"
 #include "hw/boards.h"
 #include "sysemu/kvm.h"
+#include "migration/misc.h"
+#include "migration/migration.h"
 #include "trace.h"
 
 /*
@@ -75,11 +77,18 @@ static bool dirtylimit_quit;
 
 static void vcpu_dirty_rate_stat_collect(void)
 {
+    MigrationState *s = migrate_get_current();
     VcpuStat stat;
     int i = 0;
+    int64_t period = DIRTYLIMIT_CALC_TIME_MS;
+
+    if (migrate_dirty_limit() &&
+        migration_is_active(s)) {
+        period = s->parameters.x_vcpu_dirty_limit_period;
+    }
 
     /* calculate vcpu dirtyrate */
-    vcpu_calculate_dirtyrate(DIRTYLIMIT_CALC_TIME_MS,
+    vcpu_calculate_dirtyrate(period,
                              &stat,
                              GLOBAL_DIRTY_LIMIT,
                              false);
-- 
1.8.3.1