Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755976Ab1EDUxO (ORCPT ); Wed, 4 May 2011 16:53:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34790 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755860Ab1EDUxM (ORCPT ); Wed, 4 May 2011 16:53:12 -0400 Date: Wed, 4 May 2011 23:52:33 +0300 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Rusty Russell , Carsten Otte , Christian Borntraeger , linux390@de.ibm.com, Martin Schwidefsky , Heiko Carstens , Shirley Ma , lguest@lists.ozlabs.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, Krishna Kumar , Tom Lendacky , steved@us.ibm.com, habanero@linux.vnet.ibm.com Subject: [PATCH 14/18] virtio: add api for delayed callbacks Message-ID: <64d47c628b3fdc0ac156aed4be182933d8bcc0db.1304541919.git.mst@redhat.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mutt-Fcc: =sent User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3085 Lines: 83 Add an API that tells the other side that callbacks should be delayed until a lot of work has been done. Implement using the new used_event feature. Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_ring.c | 27 +++++++++++++++++++++++++++ include/linux/virtio.h | 9 +++++++++ 2 files changed, 36 insertions(+), 0 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 262dfe6..3a70d70 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -397,6 +397,33 @@ bool virtqueue_enable_cb(struct virtqueue *_vq) } EXPORT_SYMBOL_GPL(virtqueue_enable_cb); +bool virtqueue_enable_cb_delayed(struct virtqueue *_vq) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + int bufs; + + START_USE(vq); + + /* We optimistically turn back on interrupts, then check if there was + * more to do. */ + /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to + * either clear the flags bit or point the event index at the next + * entry. Always do both to keep code simple. */ + vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; + /* TODO: tune this threshold */ + bufs = (vq->vring.avail->idx - vq->last_used_idx) * 3 / 4; + vring_used_event(&vq->vring) = vq->last_used_idx + bufs; + virtio_mb(); + if (unlikely(vq->vring.used->idx - vq->last_used_idx > bufs)) { + END_USE(vq); + return false; + } + + END_USE(vq); + return true; +} +EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed); + void *virtqueue_detach_unused_buf(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 718336b..5151fd1 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -51,6 +51,13 @@ struct virtqueue { * This re-enables callbacks; it returns "false" if there are pending * buffers in the queue, to detect a possible race between the driver * checking for more work, and enabling callbacks. + * virtqueue_enable_cb_delayed: restart callbacks after disable_cb. + * vq: the struct virtqueue we're talking about. + * This re-enables callbacks but hints to the other side to delay + * interrupts until most of the available buffers have been processed; + * it returns "false" if there are many pending buffers in the queue, + * to detect a possible race between the driver checking for more work, + * and enabling callbacks. * virtqueue_detach_unused_buf: detach first unused buffer * vq: the struct virtqueue we're talking about. * Returns NULL or the "data" token handed to add_buf @@ -86,6 +93,8 @@ void virtqueue_disable_cb(struct virtqueue *vq); bool virtqueue_enable_cb(struct virtqueue *vq); +bool virtqueue_enable_cb_delayed(struct virtqueue *vq); + void *virtqueue_detach_unused_buf(struct virtqueue *vq); /** -- 1.7.5.53.gc233e -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/