During live migration, if the latency between sender and receiver
is high and bandwidth is also high (a long and fat pipe), using a bigger
packet size can help reduce migration total time. In addition, Intel
DSA offloading performs better with a large batch task. Providing an
option to set the packet size is useful for performance tuning.

Set the option:
migrate_set_parameter multifd-packet-size 4190208

Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
---
 migration/migration-hmp-cmds.c | 7 +++++++
 migration/multifd-zlib.c       | 6 ++++--
 migration/multifd-zstd.c       | 6 ++++--
 migration/multifd.c            | 6 ++++--
 migration/multifd.h            | 3 ---
 5 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
index 8219d112d6..272b553c3a 100644
--- a/migration/migration-hmp-cmds.c
+++ b/migration/migration-hmp-cmds.c
@@ -338,6 +338,9 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict *qdict)
         monitor_printf(mon, "%s: %s\n",
             MigrationParameter_str(MIGRATION_PARAMETER_BLOCK_INCREMENTAL),
             params->block_incremental ? "on" : "off");
+        monitor_printf(mon, "%s: %" PRIu64 "\n",
+            MigrationParameter_str(MIGRATION_PARAMETER_MULTIFD_PACKET_SIZE),
+            params->multifd_packet_size);
         monitor_printf(mon, "%s: %u\n",
             MigrationParameter_str(MIGRATION_PARAMETER_MULTIFD_CHANNELS),
             params->multifd_channels);
@@ -626,6 +629,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict)
         p->multifd_dsa_accel->type = QTYPE_QSTRING;
         visit_type_str(v, param, &p->multifd_dsa_accel->u.s, &err);
         break;
+    case MIGRATION_PARAMETER_MULTIFD_PACKET_SIZE:
+        p->has_multifd_packet_size = true;
+        visit_type_size(v, param, &p->multifd_packet_size, &err);
+        break;
     case MIGRATION_PARAMETER_MULTIFD_CHANNELS:
         p->has_multifd_channels = true;
         visit_type_uint8(v, param, &p->multifd_channels, &err);
diff --git a/migration/multifd-zlib.c b/migration/multifd-zlib.c
index 37ce48621e..4318ccced8 100644
--- a/migration/multifd-zlib.c
+++ b/migration/multifd-zlib.c
@@ -49,6 +49,7 @@ static int zlib_send_setup(MultiFDSendParams *p, Error **errp)
     struct zlib_data *z = g_new0(struct zlib_data, 1);
     z_stream *zs = &z->zs;
     const char *err_msg;
+    uint64_t multifd_packet_size = migrate_multifd_packet_size();
 
     zs->zalloc = Z_NULL;
     zs->zfree = Z_NULL;
@@ -58,7 +59,7 @@ static int zlib_send_setup(MultiFDSendParams *p, Error **errp)
         goto err_free_z;
     }
     /* This is the maximum size of the compressed buffer */
-    z->zbuff_len = compressBound(MULTIFD_PACKET_SIZE);
+    z->zbuff_len = compressBound(multifd_packet_size);
     z->zbuff = g_try_malloc(z->zbuff_len);
     if (!z->zbuff) {
         err_msg = "out of memory for zbuff";
@@ -186,6 +187,7 @@ static int zlib_send_prepare(MultiFDSendParams *p, Error **errp)
  */
 static int zlib_recv_setup(MultiFDRecvParams *p, Error **errp)
 {
+    uint64_t multifd_packet_size = migrate_multifd_packet_size();
     struct zlib_data *z = g_new0(struct zlib_data, 1);
     z_stream *zs = &z->zs;
 
@@ -200,7 +202,7 @@ static int zlib_recv_setup(MultiFDRecvParams *p, Error **errp)
         return -1;
     }
     /* To be safe, we reserve twice the size of the packet */
-    z->zbuff_len = MULTIFD_PACKET_SIZE * 2;
+    z->zbuff_len = multifd_packet_size * 2;
     z->zbuff = g_try_malloc(z->zbuff_len);
     if (!z->zbuff) {
         inflateEnd(zs);
diff --git a/migration/multifd-zstd.c b/migration/multifd-zstd.c
index b471daadcd..a6fdb2ac11 100644
--- a/migration/multifd-zstd.c
+++ b/migration/multifd-zstd.c
@@ -49,6 +49,7 @@ struct zstd_data {
  */
 static int zstd_send_setup(MultiFDSendParams *p, Error **errp)
 {
+    uint64_t multifd_packet_size = migrate_multifd_packet_size();
     struct zstd_data *z = g_new0(struct zstd_data, 1);
     int res;
 
@@ -69,7 +70,7 @@ static int zstd_send_setup(MultiFDSendParams *p, Error **errp)
         return -1;
     }
     /* This is the maximum size of the compressed buffer */
-    z->zbuff_len = ZSTD_compressBound(MULTIFD_PACKET_SIZE);
+    z->zbuff_len = ZSTD_compressBound(multifd_packet_size);
     z->zbuff = g_try_malloc(z->zbuff_len);
     if (!z->zbuff) {
         ZSTD_freeCStream(z->zcs);
@@ -175,6 +176,7 @@ static int zstd_send_prepare(MultiFDSendParams *p, Error **errp)
  */
 static int zstd_recv_setup(MultiFDRecvParams *p, Error **errp)
 {
+    uint64_t multifd_packet_size = migrate_multifd_packet_size();
     struct zstd_data *z = g_new0(struct zstd_data, 1);
     int ret;
 
@@ -196,7 +198,7 @@ static int zstd_recv_setup(MultiFDRecvParams *p, Error **errp)
     }
 
     /* To be safe, we reserve twice the size of the packet */
-    z->zbuff_len = MULTIFD_PACKET_SIZE * 2;
+    z->zbuff_len = multifd_packet_size * 2;
     z->zbuff = g_try_malloc(z->zbuff_len);
     if (!z->zbuff) {
         ZSTD_freeDStream(z->zds);
diff --git a/migration/multifd.c b/migration/multifd.c
index cfae5401a9..700fb1c034 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -1046,7 +1046,8 @@ static void multifd_new_send_channel_create(gpointer opaque)
 int multifd_save_setup(Error **errp)
 {
     int thread_count;
-    uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
+    uint32_t page_count =
+        migrate_multifd_packet_size() / qemu_target_page_size();
     uint8_t i;
     const char *dsa_parameter = migrate_multifd_dsa_accel();
     int ret;
@@ -1327,7 +1328,8 @@ static void *multifd_recv_thread(void *opaque)
 int multifd_load_setup(Error **errp)
 {
     int thread_count;
-    uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
+    uint32_t page_count =
+        migrate_multifd_packet_size() / qemu_target_page_size();
     uint8_t i;
     const char *dsa_parameter = migrate_multifd_dsa_accel();
     int ret;
diff --git a/migration/multifd.h b/migration/multifd.h
index 97b5f888a7..4f30b24832 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -34,9 +34,6 @@ int multifd_queue_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset);
 #define MULTIFD_FLAG_ZLIB (1 << 1)
 #define MULTIFD_FLAG_ZSTD (2 << 1)
 
-/* This value needs to be a multiple of qemu_target_page_size() */
-#define MULTIFD_PACKET_SIZE (512 * 1024)
-
 typedef struct {
     uint32_t magic;
     uint32_t version;
-- 
2.30.2