qemu/migration-Introduce-dirty-limit-capability.patch

From c7ae0b39eec728d7f88029f932fdd6d3bfda6e68 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hyman=20Huang=28=E9=BB=84=E5=8B=87=29?=
 <yong.huang@smartx.com>
Date: Wed, 7 Jun 2023 23:30:50 +0800
Subject: [PATCH] migration: Introduce dirty-limit capability
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

There is a conflict when merging patches in qemu-6.2.0, and there is a phenomenon that the corresponding files and functions cannot be found.Merge after modifying the patch by wangguochun@kylinos.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
migrate-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) <yong.huang@smartx.com>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-Id: <168618975839.6361.17407633874747688653-4@git.sr.ht>
Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 migration/migration.c | 25 +++++++++++++++++++++++++
 migration/migration.h |  1 +
 qapi/migration.json   | 13 ++++++++++++-
 softmmu/dirtylimit.c  | 17 +++++++++++++----
 4 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 06d9b6a15d..50c33fecf3 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -60,6 +60,7 @@
 #include "qemu/yank.h"
 #include "sysemu/cpus.h"
 #include "yank_functions.h"
+#include "sysemu/kvm.h"
 
 #define MAX_THROTTLE  (128 << 20)      /* Migration transfer speed throttling */
 
@@ -1265,6 +1266,20 @@ static bool migrate_caps_check(bool *cap_list,
         error_setg(errp, "multifd is not supported by current protocol");
         return false;
     }
+    
+    if (cap_list[MIGRATION_CAPABILITY_DIRTY_LIMIT]) {
+        if (cap_list[MIGRATION_CAPABILITY_AUTO_CONVERGE]) {
+            error_setg(errp, "dirty-limit conflicts with auto-converge"
+                       " either of then available currently");
+            return false;
+        }
+
+        if (!kvm_enabled() || !kvm_dirty_ring_enabled()) {
+            error_setg(errp, "dirty-limit requires KVM with accelerator"
+                   " property 'dirty-ring-size' set");
+            return false;
+        }
+    }
 
     return true;
 }
@@ -2550,6 +2565,15 @@ bool migrate_dirty_bitmaps(void)
     return s->enabled_capabilities[MIGRATION_CAPABILITY_DIRTY_BITMAPS];
 }
 
+bool migrate_dirty_limit(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_DIRTY_LIMIT];
+}
+
 bool migrate_ignore_shared(void)
 {
     MigrationState *s;
@@ -4316,6 +4340,7 @@ static Property migration_properties[] = {
     DEFINE_PROP_UINT64("vcpu-dirty-limit", MigrationState,
                        parameters.vcpu_dirty_limit,
                        DEFAULT_MIGRATE_VCPU_DIRTY_LIMIT),
+    DEFINE_PROP_MIG_CAP("x-dirty-limit", MIGRATION_CAPABILITY_DIRTY_LIMIT),
 
     /* Migration capabilities */
     DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
diff --git a/migration/migration.h b/migration/migration.h
index 6b546a6ac7..9ce1fc8ea0 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -329,6 +329,7 @@ bool migrate_release_ram(void);
 bool migrate_postcopy_ram(void);
 bool migrate_zero_blocks(void);
 bool migrate_dirty_bitmaps(void);
+bool migrate_dirty_limit(void);
 bool migrate_ignore_shared(void);
 bool migrate_validate_uuid(void);
 
diff --git a/qapi/migration.json b/qapi/migration.json
index f35f0377dc..4751c5ee53 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -452,6 +452,16 @@
 #                       procedure starts. The VM RAM is saved with running VM.
 #                       (since 6.0)
 #
+# @dirty-limit: If enabled, migration will use the dirty-limit algo to
+#               throttle down guest instead of auto-converge algo.
+#               Throttle algo only works when vCPU's dirtyrate greater
+#               than 'vcpu-dirty-limit', read processes in guest os
+#               aren't penalized any more, so this algo can improve
+#               performance of vCPU during live migration. This is an
+#               optional performance feature and should not affect the
+#               correctness of the existing auto-converge algo.
+#               (since 8.1)
+#
 # Features:
 # @unstable: Members @x-colo and @x-ignore-shared are experimental.
 #
@@ -465,7 +475,8 @@
            'block', 'return-path', 'pause-before-switchover', 'multifd',
            'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
            { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
-           'validate-uuid', 'background-snapshot'] }
+           'validate-uuid', 'background-snapshot',
+           'dirty-limit'] }
 
 ##
 # @MigrationCapabilityStatus:
diff --git a/softmmu/dirtylimit.c b/softmmu/dirtylimit.c
index 5041c230d0..4d770aaba4 100644
--- a/softmmu/dirtylimit.c
+++ b/softmmu/dirtylimit.c
@@ -24,6 +24,8 @@
 #include "hw/boards.h"
 #include "sysemu/kvm.h"
 #include "trace.h"
+#include "migration/misc.h"
+#include "migration/migration.h"
 
 /*
  * Dirtylimit stop working if dirty page rate error
@@ -75,14 +77,21 @@ 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,
-                             &stat,
-                             GLOBAL_DIRTY_LIMIT,
-                             false);
+    vcpu_calculate_dirtyrate(period,
+                              &stat,
+                              GLOBAL_DIRTY_LIMIT,
+                              false);
 
     for (i = 0; i < stat.nvcpu; i++) {
         vcpu_dirty_rate_stat->stat.rates[i].id = i;
-- 
2.27.0