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authorPeter Xu <peterx@redhat.com>2022-01-19 16:09:18 +0800
committerJuan Quintela <quintela@redhat.com>2022-01-28 15:38:23 +0100
commita1fe28df7547120bc3ac8bc4c3d1565d4cf7905e (patch)
tree6a6d1a744b0a3e8ab395ed090f68263458acf10d
parent2d1c37c603ab3ed9ec1abfc4f4491b8680b23a77 (diff)
migration: Add postcopy_has_request()
Add a helper to detect whether postcopy has pending request. Since at it, cleanup the code a bit, e.g. in unqueue_page() we shouldn't need to check it again on queue empty because we're the only one (besides cleanup code, which should never run during this process) that will take a request off the list, so the request list can only grow but not shrink under the hood. Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>
-rw-r--r--migration/ram.c45
1 files changed, 28 insertions, 17 deletions
diff --git a/migration/ram.c b/migration/ram.c
index 58adcaf430..eb9db4f777 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -355,6 +355,12 @@ static RAMState *ram_state;
static NotifierWithReturnList precopy_notifier_list;
+/* Whether postcopy has queued requests? */
+static bool postcopy_has_request(RAMState *rs)
+{
+ return !QSIMPLEQ_EMPTY_ATOMIC(&rs->src_page_requests);
+}
+
void precopy_infrastructure_init(void)
{
notifier_with_return_list_init(&precopy_notifier_list);
@@ -1539,28 +1545,33 @@ static bool find_dirty_block(RAMState *rs, PageSearchStatus *pss, bool *again)
*/
static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset)
{
+ struct RAMSrcPageRequest *entry;
RAMBlock *block = NULL;
- if (QSIMPLEQ_EMPTY_ATOMIC(&rs->src_page_requests)) {
+ if (!postcopy_has_request(rs)) {
return NULL;
}
QEMU_LOCK_GUARD(&rs->src_page_req_mutex);
- if (!QSIMPLEQ_EMPTY(&rs->src_page_requests)) {
- struct RAMSrcPageRequest *entry =
- QSIMPLEQ_FIRST(&rs->src_page_requests);
- block = entry->rb;
- *offset = entry->offset;
-
- if (entry->len > TARGET_PAGE_SIZE) {
- entry->len -= TARGET_PAGE_SIZE;
- entry->offset += TARGET_PAGE_SIZE;
- } else {
- memory_region_unref(block->mr);
- QSIMPLEQ_REMOVE_HEAD(&rs->src_page_requests, next_req);
- g_free(entry);
- migration_consume_urgent_request();
- }
+
+ /*
+ * This should _never_ change even after we take the lock, because no one
+ * should be taking anything off the request list other than us.
+ */
+ assert(postcopy_has_request(rs));
+
+ entry = QSIMPLEQ_FIRST(&rs->src_page_requests);
+ block = entry->rb;
+ *offset = entry->offset;
+
+ if (entry->len > TARGET_PAGE_SIZE) {
+ entry->len -= TARGET_PAGE_SIZE;
+ entry->offset += TARGET_PAGE_SIZE;
+ } else {
+ memory_region_unref(block->mr);
+ QSIMPLEQ_REMOVE_HEAD(&rs->src_page_requests, next_req);
+ g_free(entry);
+ migration_consume_urgent_request();
}
return block;
@@ -2992,7 +3003,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
i = 0;
while ((ret = qemu_file_rate_limit(f)) == 0 ||
- !QSIMPLEQ_EMPTY(&rs->src_page_requests)) {
+ postcopy_has_request(rs)) {
int pages;
if (qemu_file_get_error(f)) {