From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [RFC 1/2] virtio-ring: Use threshold for switching to indirect descriptors Date: Mon, 18 Jun 2012 16:09:57 +0200 Message-ID: <1340028598-10142-1-git-send-email-levinsasha928@gmail.com> Cc: virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Sasha Levin To: mst@redhat.com, asias@redhat.com, stefanha@gmail.com Return-path: Received: from mail-ob0-f174.google.com ([209.85.214.174]:54752 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750756Ab2FROJN (ORCPT ); Mon, 18 Jun 2012 10:09:13 -0400 Received: by obbtb18 with SMTP id tb18so8523905obb.19 for ; Mon, 18 Jun 2012 07:09:12 -0700 (PDT) Sender: kvm-owner@vger.kernel.org List-ID: Currently if VIRTIO_RING_F_INDIRECT_DESC is enabled we will use indirect descriptors even if we have plenty of space in the ring. This means that we take a performance hit at all times due to the overhead of creating indirect descriptors. Instead, use it only after we're below a configurable offset. Signed-off-by: Sasha Levin --- drivers/block/virtio_blk.c | 4 ++++ drivers/char/hw_random/virtio-rng.c | 4 ++++ drivers/char/virtio_console.c | 4 ++++ drivers/net/virtio_net.c | 4 ++++ drivers/virtio/virtio_balloon.c | 4 ++++ drivers/virtio/virtio_ring.c | 21 +++++++++++++++------ include/linux/virtio.h | 1 + net/9p/trans_virtio.c | 4 ++++ 8 files changed, 40 insertions(+), 6 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 693187d..a2c8d97 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -19,6 +19,9 @@ static DEFINE_IDA(vd_index_ida); struct workqueue_struct *virtblk_wq; +static unsigned int indirect_thresh = 0; +module_param(indirect_thresh, uint, S_IRUGO); + struct virtio_blk { spinlock_t lock; @@ -438,6 +441,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) mutex_init(&vblk->config_lock); INIT_WORK(&vblk->config_work, virtblk_config_changed_work); vblk->config_enable = true; + vdev->indirect_thresh = indirect_thresh; err = init_vq(vblk); if (err) diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c index 723725b..bcaddb9 100644 --- a/drivers/char/hw_random/virtio-rng.c +++ b/drivers/char/hw_random/virtio-rng.c @@ -25,6 +25,9 @@ #include #include +static unsigned int indirect_thresh = 0; +module_param(indirect_thresh, uint, S_IRUGO); + static struct virtqueue *vq; static unsigned int data_avail; static DECLARE_COMPLETION(have_data); @@ -90,6 +93,7 @@ static int virtrng_probe(struct virtio_device *vdev) int err; /* We expect a single virtqueue. */ + vdev->indirect_thresh = indirect_thresh; vq = virtio_find_single_vq(vdev, random_recv_done, "input"); if (IS_ERR(vq)) return PTR_ERR(vq); diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index cdf2f54..60397a4 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -37,6 +37,9 @@ #include #include "../tty/hvc/hvc_console.h" +static unsigned int indirect_thresh = 0; +module_param(indirect_thresh, uint, S_IRUGO); + /* * This is a global struct for storing common data for all the devices * this driver handles. @@ -1729,6 +1732,7 @@ static int __devinit virtcons_probe(struct virtio_device *vdev) max_nr_ports), &portdev->config.max_nr_ports) == 0) multiport = true; + vdev->indirect_thresh = indirect_thresh; err = init_vqs(portdev); if (err < 0) { diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index f18149a..5c1be92 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -34,6 +34,9 @@ static bool csum = true, gso = true; module_param(csum, bool, 0444); module_param(gso, bool, 0444); +static unsigned int indirect_thresh = 0; +module_param(indirect_thresh, uint, S_IRUGO); + /* FIXME: MTU in config. */ #define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN) #define GOOD_COPY_LEN 128 @@ -1128,6 +1131,7 @@ static int virtnet_probe(struct virtio_device *vdev) if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) vi->mergeable_rx_bufs = true; + vdev->indirect_thresh = indirect_thresh; err = init_vqs(vi); if (err) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index bfbc15c..4fc11ba 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -35,6 +35,9 @@ */ #define VIRTIO_BALLOON_PAGES_PER_PAGE (PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT) +static unsigned int indirect_thresh = 0; +module_param(indirect_thresh, uint, S_IRUGO); + struct virtio_balloon { struct virtio_device *vdev; @@ -360,6 +363,7 @@ static int virtballoon_probe(struct virtio_device *vdev) init_waitqueue_head(&vb->config_change); vb->vdev = vdev; vb->need_stats_update = 0; + vdev->indirect_thresh = indirect_thresh; err = init_vqs(vb); if (err) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 5aa43c3..99a64a7 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -87,8 +87,11 @@ struct vring_virtqueue /* Other side has made a mess, don't try any more. */ bool broken; - /* Host supports indirect buffers */ - bool indirect; + /* + * Min. number of free space in the ring to trigger direct + * descriptor use + */ + unsigned int indirect_thresh; /* Host publishes avail event idx */ bool event; @@ -216,9 +219,12 @@ int virtqueue_add_buf(struct virtqueue *_vq, } #endif - /* If the host supports indirect descriptor tables, and we have multiple - * buffers, then go indirect. FIXME: tune this threshold */ - if (vq->indirect && (out + in) > 1 && vq->num_free) { + /* + * If the host supports indirect descriptor tables, and we have multiple + * buffers, then go indirect. + */ + if ((out + in) > 1 && vq->num_free && + (vq->num_free < vq->indirect_thresh)) { head = vring_add_indirect(vq, sg, out, in, gfp); if (likely(head >= 0)) goto add_head; @@ -647,13 +653,16 @@ struct virtqueue *vring_new_virtqueue(unsigned int num, vq->broken = false; vq->last_used_idx = 0; vq->num_added = 0; + vq->indirect_thresh = 0; list_add_tail(&vq->vq.list, &vdev->vqs); #ifdef DEBUG vq->in_use = false; vq->last_add_time_valid = false; #endif - vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC); + if (virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC)) + vq->indirect_thresh = vdev->indirect_thresh; + vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); /* No callback? Tell other side not to bother us. */ diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 8efd28a..36019ec 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -69,6 +69,7 @@ struct virtio_device { /* Note that this is a Linux set_bit-style bitmap. */ unsigned long features[1]; void *priv; + unsigned int indirect_thresh; }; #define dev_to_virtio(dev) container_of(dev, struct virtio_device, dev) diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index 5af18d1..357bfba 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -52,6 +52,9 @@ #define VIRTQUEUE_NUM 128 +static unsigned int indirect_thresh = 0; +module_param(indirect_thresh, uint, S_IRUGO); + /* a single mutex to manage channel initialization and attachment */ static DEFINE_MUTEX(virtio_9p_lock); static DECLARE_WAIT_QUEUE_HEAD(vp_wq); @@ -501,6 +504,7 @@ static int p9_virtio_probe(struct virtio_device *vdev) chan->vdev = vdev; /* We expect one virtqueue, for requests. */ + vdev->indirect_thresh = indirect_thresh; chan->vq = virtio_find_single_vq(vdev, req_done, "requests"); if (IS_ERR(chan->vq)) { err = PTR_ERR(chan->vq); -- 1.7.8.6