Re: [Qemu-devel] [PATCH v2 5/5] migration: Stop rdma yielding during incoming postcopy

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Lidong Chen (jemmy858585@gmail.com) wrote:
> During incoming postcopy, the destination qemu will invoke
> qemu_rdma_wait_comp_channel in a seprate thread. So does not use rdma
> yield, and poll the completion channel fd instead.
> 
> Signed-off-by: Lidong Chen <lidongchen@tencent.com>

OK, I think so; it's a bit delicate, but I can't currently see a better
way.


Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/rdma.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/rdma.c b/migration/rdma.c
> index 0652224..4ba9fe2 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -1490,11 +1490,13 @@ static int qemu_rdma_wait_comp_channel(RDMAContext *rdma)
>       * Coroutine doesn't start until migration_fd_process_incoming()
>       * so don't yield unless we know we're running inside of a coroutine.
>       */
> -    if (rdma->migration_started_on_destination) {
> +    if (rdma->migration_started_on_destination &&
> +        migration_incoming_get_current()->state == MIGRATION_STATUS_ACTIVE) {
>          yield_until_fd_readable(rdma->comp_channel->fd);
>      } else {
>          /* This is the source side, we're in a separate thread
>           * or destination prior to migration_fd_process_incoming()
> +         * after postcopy, the destination also in a seprate thread.
>           * we can't yield; so we have to poll the fd.
>           * But we need to be able to handle 'cancel' or an error
>           * without hanging forever.
> -- 
> 1.8.3.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK