@@ -2470,6 +2470,7 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss)
unsigned long hostpage_boundary =
QEMU_ALIGN_UP(pss->page + 1, pagesize_bits);
unsigned long start_page = pss->page;
+ bool page_dirty;
int res;
if (ramblock_is_ignored(pss->block)) {
@@ -2487,22 +2488,41 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss)
break;
}
+ page_dirty = migration_bitmap_clear_dirty(rs, pss->block, pss->page);
+ /*
+ * Properly yield the lock only in postcopy preempt mode because
+ * both migration thread and rp-return thread can operate on the
+ * bitmaps.
+ */
+ if (postcopy_preempt_active()) {
+ qemu_mutex_unlock(&rs->bitmap_mutex);
+ }
+
/* Check the pages is dirty and if it is send it */
- if (migration_bitmap_clear_dirty(rs, pss->block, pss->page)) {
+ if (page_dirty) {
tmppages = ram_save_target_page(rs, pss);
- if (tmppages < 0) {
- return tmppages;
+ if (tmppages >= 0) {
+ pages += tmppages;
+ /*
+ * Allow rate limiting to happen in the middle of huge pages if
+ * something is sent in the current iteration.
+ */
+ if (pagesize_bits > 1 && tmppages > 0) {
+ migration_rate_limit();
+ }
}
+ } else {
+ tmppages = 0;
+ }
- pages += tmppages;
- /*
- * Allow rate limiting to happen in the middle of huge pages if
- * something is sent in the current iteration.
- */
- if (pagesize_bits > 1 && tmppages > 0) {
- migration_rate_limit();
- }
+ if (postcopy_preempt_active()) {
+ qemu_mutex_lock(&rs->bitmap_mutex);
}
+
+ if (tmppages < 0) {
+ return tmppages;
+ }
+
pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
} while ((pss->page < hostpage_boundary) &&
offset_in_ramblock(pss->block,
Don't take the bitmap mutex when sending pages, or when being throttled by migration_rate_limit() (which is a bit tricky to call it here in ram code, but seems still helpful). It prepares for the possibility of concurrently sending pages in >1 threads using the function ram_save_host_page() because all threads may need the bitmap_mutex to operate on bitmaps, so that either sendmsg() or any kind of qemu_sem_wait() blocking for one thread will not block the other from progressing. Signed-off-by: Peter Xu <peterx@redhat.com> --- migration/ram.c | 42 +++++++++++++++++++++++++++++++----------- 1 file changed, 31 insertions(+), 11 deletions(-)