Commit ae526e32 authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Juan Quintela
Browse files

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: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@tencent.com>
Reviewed-by: default avatarJuan Quintela <quintela@redhat.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
parent 5e5fdcff

include/qemu/queue.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

migration/ram.c

+4 −0
Original line number Diff line number Diff line
@@ -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 =