Multifd sender thread performs zero page checking. If a page is
a zero page, only the page's metadata is sent to the receiver.
If a page is a normal page, the entire page's content is sent to
the receiver. This change adds a test hook to set the normal page
ratio. A zero page will be forced to be sent as a normal page. This
is useful for live migration performance analysis and optimization.

Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
---
 migration/options.c | 31 +++++++++++++++++++++++++++++++
 migration/options.h |  1 +
 qapi/migration.json | 18 +++++++++++++++---
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/migration/options.c b/migration/options.c
index 6e424b5d63..e7f1e2df24 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -79,6 +79,11 @@
 #define DEFAULT_MIGRATE_ANNOUNCE_ROUNDS    5
 #define DEFAULT_MIGRATE_ANNOUNCE_STEP    100
 
+/*
+ * Parameter for multifd normal page test hook.
+ */
+#define DEFAULT_MIGRATE_MULTIFD_NORMAL_PAGE_RATIO 101
+
 #define DEFINE_PROP_MIG_CAP(name, x)             \
     DEFINE_PROP_BOOL(name, MigrationState, capabilities[x], false)
 
@@ -181,6 +186,9 @@ Property migration_properties[] = {
                       MIG_MODE_NORMAL),
     DEFINE_PROP_STRING("multifd-dsa-accel", MigrationState,
                        parameters.multifd_dsa_accel),
+    DEFINE_PROP_UINT8("multifd-normal-page-ratio", MigrationState,
+                      parameters.multifd_normal_page_ratio,
+                      DEFAULT_MIGRATE_MULTIFD_NORMAL_PAGE_RATIO),
 
     /* Migration capabilities */
     DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
@@ -860,6 +868,12 @@ int migrate_multifd_channels(void)
     return s->parameters.multifd_channels;
 }
 
+uint8_t migrate_multifd_normal_page_ratio(void)
+{
+    MigrationState *s = migrate_get_current();
+    return s->parameters.multifd_normal_page_ratio;
+}
+
 MultiFDCompression migrate_multifd_compression(void)
 {
     MigrationState *s = migrate_get_current();
@@ -1258,6 +1272,14 @@ bool migrate_params_check(MigrationParameters *params, Error **errp)
         return false;
     }
 
+    if (params->has_multifd_normal_page_ratio &&
+        params->multifd_normal_page_ratio > 100) {
+        error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
+                   "multifd_normal_page_ratio",
+                   "a value between 0 and 100");
+        return false;
+    }
+
     return true;
 }
 
@@ -1378,6 +1400,11 @@ static void migrate_params_test_apply(MigrateSetParameters *params,
         assert(params->multifd_dsa_accel->type == QTYPE_QSTRING);
         dest->multifd_dsa_accel = params->multifd_dsa_accel->u.s;
     }
+
+    if (params->has_multifd_normal_page_ratio) {
+        dest->has_multifd_normal_page_ratio = true;
+        dest->multifd_normal_page_ratio = params->multifd_normal_page_ratio;
+    }
 }
 
 static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
@@ -1528,6 +1555,10 @@ static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
         assert(params->multifd_dsa_accel->type == QTYPE_QSTRING);
         s->parameters.multifd_dsa_accel = g_strdup(params->multifd_dsa_accel->u.s);
     }
+
+    if (params->has_multifd_normal_page_ratio) {
+        s->parameters.multifd_normal_page_ratio = params->multifd_normal_page_ratio;
+    }
 }
 
 void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp)
diff --git a/migration/options.h b/migration/options.h
index 56100961a9..21e3e7b0cf 100644
--- a/migration/options.h
+++ b/migration/options.h
@@ -95,6 +95,7 @@ const char *migrate_tls_creds(void);
 const char *migrate_tls_hostname(void);
 uint64_t migrate_xbzrle_cache_size(void);
 const char *migrate_multifd_dsa_accel(void);
+uint8_t migrate_multifd_normal_page_ratio(void);
 
 /* parameters setters */
 
diff --git a/qapi/migration.json b/qapi/migration.json
index a8e3b66d6f..bb876c8325 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -882,6 +882,9 @@
 # @multifd-dsa-accel: If enabled, use DSA accelerator offloading for
 #                     certain memory operations. (since 8.2)
 #
+# @multifd-normal-page-ratio: Test hook setting the normal page ratio.
+#     (Since 8.2)
+#
 # Features:
 #
 # @deprecated: Member @block-incremental is deprecated.  Use
@@ -915,7 +918,8 @@
            'block-bitmap-mapping',
            { 'name': 'x-vcpu-dirty-limit-period', 'features': ['unstable'] },
            'vcpu-dirty-limit',
-           'mode'] }
+           'mode',
+           'multifd-normal-page-ratio'] }
 
 ##
 # @MigrateSetParameters:
@@ -1073,6 +1077,9 @@
 # @multifd-dsa-accel: If enabled, use DSA accelerator offloading for
 #                     certain memory operations. (since 8.2)
 #
+# @multifd-normal-page-ratio: Test hook setting the normal page ratio.
+#     (Since 8.2)
+#
 # Features:
 #
 # @deprecated: Member @block-incremental is deprecated.  Use
@@ -1127,7 +1134,8 @@
                                             'features': [ 'unstable' ] },
             '*vcpu-dirty-limit': 'uint64',
             '*mode': 'MigMode',
-            '*multifd-dsa-accel': 'StrOrNull'} }
+            '*multifd-dsa-accel': 'StrOrNull',
+            '*multifd-normal-page-ratio': 'uint8'} }
 
 ##
 # @migrate-set-parameters:
@@ -1305,6 +1313,9 @@
 # @multifd-dsa-accel: If enabled, use DSA accelerator offloading for
 #                     certain memory operations. (since 8.2)
 #
+# @multifd-normal-page-ratio: Test hook setting the normal page ratio.
+#     (Since 8.2)
+#
 # Features:
 #
 # @deprecated: Member @block-incremental is deprecated.  Use
@@ -1356,7 +1367,8 @@
                                             'features': [ 'unstable' ] },
             '*vcpu-dirty-limit': 'uint64',
             '*mode': 'MigMode',
-            '*multifd-dsa-accel': 'str'} }
+            '*multifd-dsa-accel': 'str',
+            '*multifd-normal-page-ratio': 'uint8'} }
 
 ##
 # @query-migrate-parameters:
-- 
2.30.2