[PATCH v3 21/23] multifd: Support for zero pages transmission

[Juan Quintela <quintela@redhat.com>]

This patch adds counters and similar.  Logic will be added on the
following patch.

Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 migration/multifd.h    | 13 ++++++++++++-
 migration/multifd.c    | 22 +++++++++++++++++++---
 migration/trace-events |  2 +-
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/migration/multifd.h b/migration/multifd.h
index 39e55d7f05..973315b545 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -49,7 +49,10 @@ typedef struct {
     /* size of the next packet that contains pages */
     uint32_t next_packet_size;
     uint64_t packet_num;
-    uint64_t unused[4];    /* Reserved for future use */
+    /* zero pages */
+    uint32_t zero_pages;
+    uint32_t unused32[1];    /* Reserved for future use */
+    uint64_t unused64[3];    /* Reserved for future use */
     char ramblock[256];
     uint64_t offset[];
 } __attribute__((packed)) MultiFDPacket_t;
@@ -117,6 +120,10 @@ typedef struct {
     ram_addr_t *normal;
     /* num of non zero pages */
     uint32_t normal_num;
+    /* Pages that are  zero */
+    ram_addr_t *zero;
+    /* num of zero pages */
+    uint32_t zero_num;
     /* used for compression methods */
     void *data;
 }  MultiFDSendParams;
@@ -162,6 +169,10 @@ typedef struct {
     ram_addr_t *normal;
     /* num of non zero pages */
     uint32_t normal_num;
+    /* Pages that are  zero */
+    ram_addr_t *zero;
+    /* num of zero pages */
+    uint32_t zero_num;
     /* used for de-compression methods */
     void *data;
 } MultiFDRecvParams;
diff --git a/migration/multifd.c b/migration/multifd.c
index d1ab823f98..2e4dffd6c6 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -265,6 +265,7 @@ static void multifd_send_fill_packet(MultiFDSendParams *p)
     packet->normal_pages = cpu_to_be32(p->normal_num);
     packet->next_packet_size = cpu_to_be32(p->next_packet_size);
     packet->packet_num = cpu_to_be64(p->packet_num);
+    packet->zero_pages = cpu_to_be32(p->zero_num);
 
     if (p->pages->block) {
         strncpy(packet->ramblock, p->pages->block->idstr, 256);
@@ -327,7 +328,15 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
     p->next_packet_size = be32_to_cpu(packet->next_packet_size);
     p->packet_num = be64_to_cpu(packet->packet_num);
 
-    if (p->normal_num == 0) {
+    p->zero_num = be32_to_cpu(packet->zero_pages);
+    if (p->zero_num > packet->pages_alloc - p->normal_num) {
+        error_setg(errp, "multifd: received packet "
+                   "with %d zero pages and expected maximum pages are %d",
+                   p->normal_num, packet->pages_alloc - p->zero_num) ;
+        return -1;
+    }
+
+    if (p->normal_num == 0 && p->zero_num == 0) {
         return 0;
     }
 
@@ -550,6 +559,8 @@ void multifd_save_cleanup(void)
         p->iov = NULL;
         g_free(p->normal);
         p->normal = NULL;
+        g_free(p->zero);
+        p->zero = NULL;
         multifd_send_state->ops->send_cleanup(p, &local_err);
         if (local_err) {
             migrate_set_error(migrate_get_current(), local_err);
@@ -638,6 +649,7 @@ static void *multifd_send_thread(void *opaque)
             uint32_t flags = p->flags;
             p->iovs_num = 1;
             p->normal_num = 0;
+            p->zero_num = 0;
 
             for (int i = 0; i < p->pages->num; i++) {
                 p->normal[p->normal_num] = p->pages->offset[i];
@@ -659,8 +671,8 @@ static void *multifd_send_thread(void *opaque)
             p->pages->block = NULL;
             qemu_mutex_unlock(&p->mutex);
 
-            trace_multifd_send(p->id, packet_num, p->normal_num, flags,
-                               p->next_packet_size);
+            trace_multifd_send(p->id, packet_num, p->normal_num, p->zero_num,
+                               flags, p->next_packet_size);
 
             p->iov[0].iov_len = p->packet_len;
             p->iov[0].iov_base = p->packet;
@@ -910,6 +922,7 @@ int multifd_save_setup(Error **errp)
         /* We need one extra place for the packet header */
         p->iov = g_new0(struct iovec, page_count + 1);
         p->normal = g_new0(ram_addr_t, page_count);
+        p->zero = g_new0(ram_addr_t, page_count);
         socket_send_channel_create(multifd_new_send_channel_async, p);
     }
 
@@ -1011,6 +1024,8 @@ int multifd_load_cleanup(Error **errp)
         p->iov = NULL;
         g_free(p->normal);
         p->normal = NULL;
+        g_free(p->zero);
+        p->zero = NULL;
         multifd_recv_state->ops->recv_cleanup(p);
     }
     qemu_sem_destroy(&multifd_recv_state->sem_sync);
@@ -1150,6 +1165,7 @@ int multifd_load_setup(Error **errp)
         p->name = g_strdup_printf("multifdrecv_%d", i);
         p->iov = g_new0(struct iovec, page_count);
         p->normal = g_new0(ram_addr_t, page_count);
+        p->zero = g_new0(ram_addr_t, page_count);
     }
 
     for (i = 0; i < thread_count; i++) {
diff --git a/migration/trace-events b/migration/trace-events
index af8dee9af0..608decbdcc 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -124,7 +124,7 @@ multifd_recv_sync_main_wait(uint8_t id) "channel %d"
 multifd_recv_terminate_threads(bool error) "error %d"
 multifd_recv_thread_end(uint8_t id, uint64_t packets, uint64_t pages) "channel %d packets %" PRIu64 " pages %" PRIu64
 multifd_recv_thread_start(uint8_t id) "%d"
-multifd_send(uint8_t id, uint64_t packet_num, uint32_t normal, uint32_t flags, uint32_t next_packet_size) "channel %d packet_num %" PRIu64 " normal pages %d flags 0x%x next packet size %d"
+multifd_send(uint8_t id, uint64_t packet_num, uint32_t normal, uint32_t zero, uint32_t flags, uint32_t next_packet_size) "channel %d packet_num %" PRIu64 " normal pages %d zero pages %d flags 0x%x next packet size %d"
 multifd_send_error(uint8_t id) "channel %d"
 multifd_send_sync_main(long packet_num) "packet num %ld"
 multifd_send_sync_main_signal(uint8_t id) "channel %d"
-- 
2.33.1