migration: discard non-dirty ram pages after the start of postcopy

After the start of postcopy migration there are some non-dirty pages which have
already been migrated. These pages are no longer needed on the source vm so that
we can free them and it doen't hurt to complete the migration.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Message-Id: <20170203152321.19739-4-pbutsykin@virtuozzo.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

diff --git a/include/migration/migration.h b/include/migration/migration.h
index b9b706a7e31522c10c8a4a343de617cc4fea83de..71ce19062cd1a6f8822ec405ac9f3a9e49ba38f6 100644 (file)
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -285,6 +285,7 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms);
 int ram_discard_range(MigrationIncomingState *mis, const char *block_name,
                       uint64_t start, size_t length);
 int ram_postcopy_incoming_init(MigrationIncomingState *mis);
+void ram_postcopy_migrated_memory_release(MigrationState *ms);
 
 /**
  * @migrate_add_blocker - prevent migration from proceeding

diff --git a/migration/migration.c b/migration/migration.c
index 68afc070167049c4eee27380416e9eaca287cd81..2a26a20aafdd1c9834629a7cad850449f42bdede 100644 (file)
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1722,6 +1722,10 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running)
      */
     qemu_savevm_send_ping(ms->to_dst_file, 4);
 
+    if (migrate_release_ram()) {
+        ram_postcopy_migrated_memory_release(ms);
+    }
+
     ret = qemu_file_get_error(ms->to_dst_file);
     if (ret) {
         error_report("postcopy_start: Migration stream errored");

diff --git a/migration/ram.c b/migration/ram.c
index c22209db30545b98a559180085426b359ad5f21c..67f2efbc593780c68278b4d352c1647a61330ed9 100644 (file)
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1537,6 +1537,25 @@ void ram_debug_dump_bitmap(unsigned long *todump, bool expected)
 
 /* **** functions for postcopy ***** */
 
+void ram_postcopy_migrated_memory_release(MigrationState *ms)
+{
+    struct RAMBlock *block;
+    unsigned long *bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
+
+    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
+        unsigned long first = block->offset >> TARGET_PAGE_BITS;
+        unsigned long range = first + (block->used_length >> TARGET_PAGE_BITS);
+        unsigned long run_start = find_next_zero_bit(bitmap, range, first);
+
+        while (run_start < range) {
+            unsigned long run_end = find_next_bit(bitmap, range, run_start + 1);
+            ram_discard_range(NULL, block->idstr, run_start << TARGET_PAGE_BITS,
+                              (run_end - run_start) << TARGET_PAGE_BITS);
+            run_start = find_next_zero_bit(bitmap, range, run_end + 1);
+        }
+    }
+}
+
 /*
  * Callback from postcopy_each_ram_send_discard for each RAMBlock
  * Note: At this point the 'unsentmap' is the processed bitmap combined