| Message ID | 1346325718-11151-1-git-send-email-levinsasha928@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Aug 30, 2012 at 01:21:57PM +0200, Sasha Levin wrote: > 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 <levinsasha928@gmail.com> Some minor comments here and for the next patch. And I think I see a bug. Otherwise looks good to me. Let's add MODULE_PARM_DESC clearly explaining that this is a debugging option and users should not touch it. We can also add this text: Min. number of free space in the ring to trigger direct descriptor use. Set to 1 to always use direct descriptors. Also maybe direct_thresh is a better name. > --- > 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 2edfb5c..7c63065 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -22,6 +22,9 @@ static DEFINE_IDA(vd_index_ida); > > struct workqueue_struct *virtblk_wq; > > +static unsigned int indirect_thresh; > +module_param(indirect_thresh, uint, S_IRUGO); > + > struct virtio_blk > { > struct virtio_device *vdev; > @@ -735,6 +738,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) > > 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 5708299..3a644f1 100644 > --- a/drivers/char/hw_random/virtio-rng.c > +++ b/drivers/char/hw_random/virtio-rng.c > @@ -25,6 +25,9 @@ > #include <linux/virtio_rng.h> > #include <linux/module.h> > > +static unsigned int indirect_thresh; > +module_param(indirect_thresh, uint, S_IRUGO); > + > static struct virtqueue *vq; > static unsigned int data_avail; > static DECLARE_COMPLETION(have_data); > @@ -93,6 +96,7 @@ static int probe_common(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 e88f843..da2e44c 100644 > --- a/drivers/char/virtio_console.c > +++ b/drivers/char/virtio_console.c > @@ -39,6 +39,9 @@ > #include <linux/module.h> > #include "../tty/hvc/hvc_console.h" > > +static unsigned int indirect_thresh; > +module_param(indirect_thresh, uint, S_IRUGO); > + > /* > * This is a global struct for storing common data for all the devices > * this driver handles. > @@ -1887,6 +1890,7 @@ 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 cbf8b06..949c89e 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 = 16; > +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 0908e60..ca5ae7a 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; > +module_param(indirect_thresh, uint, S_IRUGO); > + > struct virtio_balloon > { > struct virtio_device *vdev; > @@ -356,6 +359,7 @@ static int virtballoon_probe(struct virtio_device *vdev) > init_waitqueue_head(&vb->acked); > 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..4063e03 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. > + */ Fix comments to mention threshold. > + if ((out + in) > 1 && vq->num_free && > + (vq->num_free < vq->indirect_thresh)) { Please do not add () around conditions like this. > 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; > + cleaner else ` vq->indirect_thresh = 0; So when indirect_thresh is 0 (default) this disables indirect completely. Likely not what you wanted. Maybe the right thing to do is something like if (!indirect_thresh) vq->indirect_thresh = vq->vring.num + 1 ? > 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 a1ba8bb..48bc457 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 35b8911..418f933 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; > +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); > -- > 1.7.12 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 2edfb5c..7c63065 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -22,6 +22,9 @@ static DEFINE_IDA(vd_index_ida); struct workqueue_struct *virtblk_wq; +static unsigned int indirect_thresh; +module_param(indirect_thresh, uint, S_IRUGO); + struct virtio_blk { struct virtio_device *vdev; @@ -735,6 +738,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) 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 5708299..3a644f1 100644 --- a/drivers/char/hw_random/virtio-rng.c +++ b/drivers/char/hw_random/virtio-rng.c @@ -25,6 +25,9 @@ #include <linux/virtio_rng.h> #include <linux/module.h> +static unsigned int indirect_thresh; +module_param(indirect_thresh, uint, S_IRUGO); + static struct virtqueue *vq; static unsigned int data_avail; static DECLARE_COMPLETION(have_data); @@ -93,6 +96,7 @@ static int probe_common(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 e88f843..da2e44c 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -39,6 +39,9 @@ #include <linux/module.h> #include "../tty/hvc/hvc_console.h" +static unsigned int indirect_thresh; +module_param(indirect_thresh, uint, S_IRUGO); + /* * This is a global struct for storing common data for all the devices * this driver handles. @@ -1887,6 +1890,7 @@ 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 cbf8b06..949c89e 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 = 16; +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 0908e60..ca5ae7a 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; +module_param(indirect_thresh, uint, S_IRUGO); + struct virtio_balloon { struct virtio_device *vdev; @@ -356,6 +359,7 @@ static int virtballoon_probe(struct virtio_device *vdev) init_waitqueue_head(&vb->acked); 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..4063e03 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 a1ba8bb..48bc457 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 35b8911..418f933 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; +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);
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 <levinsasha928@gmail.com> --- 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(-)