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| author | Xiao Guangrong <xiaoguangrong@tencent.com> | 2018-08-21 16:10:25 +0800 |
|---|---|---|
| committer | Juan Quintela <quintela@redhat.com> | 2018-08-22 12:36:18 +0200 |
| commit | ae526e32bd36cfb84045c8d2fd34e0b9e39a52f8 (patch) | |
| tree | bd6083598307d47aec30506bfe26b7ec0fe4ece5 | |
| parent | 5e5fdcff28ebbba2004c6498218f506f364f1e8a (diff) | |
| download | focaccia-qemu-ae526e32bd36cfb84045c8d2fd34e0b9e39a52f8.tar.gz focaccia-qemu-ae526e32bd36cfb84045c8d2fd34e0b9e39a52f8.zip | |
migration: hold the lock only if it is really needed
Try to hold src_page_req_mutex only if the queue is not empty Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Reviewed-by: Peter Xu <peterx@redhat.com> Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>
| -rw-r--r-- | include/qemu/queue.h | 1 | ||||
| -rw-r--r-- | migration/ram.c | 4 |
2 files changed, 5 insertions, 0 deletions
diff --git a/include/qemu/queue.h b/include/qemu/queue.h index 59fd1203a1..ac418efc43 100644 --- a/include/qemu/queue.h +++ b/include/qemu/queue.h @@ -341,6 +341,7 @@ struct { \ /* * Simple queue access methods. */ +#define QSIMPLEQ_EMPTY_ATOMIC(head) (atomic_read(&((head)->sqh_first)) == NULL) #define QSIMPLEQ_EMPTY(head) ((head)->sqh_first == NULL) #define QSIMPLEQ_FIRST(head) ((head)->sqh_first) #define QSIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next) diff --git a/migration/ram.c b/migration/ram.c index 40013e68a1..79c89425a3 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -2033,6 +2033,10 @@ static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset) { RAMBlock *block = NULL; + if (QSIMPLEQ_EMPTY_ATOMIC(&rs->src_page_requests)) { + return NULL; + } + qemu_mutex_lock(&rs->src_page_req_mutex); if (!QSIMPLEQ_EMPTY(&rs->src_page_requests)) { struct RAMSrcPageRequest *entry = |