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Message-ID: <20120829153812.GD7407@redhat.com>
Date: Wed, 29 Aug 2012 18:38:12 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Sasha Levin <levinsasha928@...il.com>
Cc: rusty@...tcorp.com.au, virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, avi@...hat.com, kvm@...r.kernel.org
Subject: Re: [PATCH v2 2/2] virtio-ring: Allocate indirect buffers from cache
when possible
On Tue, Aug 28, 2012 at 03:04:03PM +0200, Sasha Levin wrote:
> Currently if VIRTIO_RING_F_INDIRECT_DESC is enabled we will
> use indirect descriptors and allocate them using a simple
> kmalloc().
>
> This patch adds a cache which will allow indirect buffers under
> a configurable size to be allocated from that cache instead.
>
> Signed-off-by: Sasha Levin <levinsasha928@...il.com>
The API is ugly - how does driver know what to set?
Is this a typical request size? Then let's call it that.
Also this is really per VQ, right?
What is a good default for net? I guess max sg?
> ---
>
> Changes in v2:
>
> - Free correctly indirect buffers.
>
> 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 | 28 ++++++++++++++++++++++++----
> include/linux/virtio.h | 1 +
> net/9p/trans_virtio.c | 5 +++++
> 8 files changed, 50 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 13b8ae9..7f670af 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -25,6 +25,9 @@ struct workqueue_struct *virtblk_wq;
> static unsigned int indirect_thresh;
> module_param(indirect_thresh, uint, S_IRUGO);
>
> +static unsigned int indirect_alloc_thresh;
> +module_param(indirect_alloc_thresh, uint, S_IRUGO);
> +
> struct virtio_blk
> {
> struct virtio_device *vdev;
> @@ -739,6 +742,7 @@ 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;
> + vdev->indirect_alloc_thresh = indirect_alloc_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 02d8421..8475ece 100644
> --- a/drivers/char/hw_random/virtio-rng.c
> +++ b/drivers/char/hw_random/virtio-rng.c
> @@ -28,6 +28,9 @@
> static unsigned int indirect_thresh;
> module_param(indirect_thresh, uint, S_IRUGO);
>
> +static unsigned int indirect_alloc_thresh;
> +module_param(indirect_alloc_thresh, uint, S_IRUGO);
> +
> static struct virtqueue *vq;
> static unsigned int data_avail;
> static DECLARE_COMPLETION(have_data);
> @@ -97,6 +100,7 @@ static int probe_common(struct virtio_device *vdev)
>
> /* We expect a single virtqueue. */
> vdev->indirect_thresh = indirect_thresh;
> + vdev->indirect_alloc_thresh = indirect_alloc_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 fc14e7f..c6f24a7 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -42,6 +42,9 @@
> static unsigned int indirect_thresh;
> module_param(indirect_thresh, uint, S_IRUGO);
>
> +static unsigned int indirect_alloc_thresh;
> +module_param(indirect_alloc_thresh, uint, S_IRUGO);
> +
> /*
> * This is a global struct for storing common data for all the devices
> * this driver handles.
> @@ -1891,6 +1894,7 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
> &portdev->config.max_nr_ports) == 0)
> multiport = true;
> vdev->indirect_thresh = indirect_thresh;
> + vdev->indirect_alloc_thresh = indirect_alloc_thresh;
>
> err = init_vqs(portdev);
> if (err < 0) {
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 64a8321..c091efd 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -37,6 +37,9 @@ module_param(gso, bool, 0444);
> static unsigned int indirect_thresh;
> module_param(indirect_thresh, uint, S_IRUGO);
>
> +static unsigned int indirect_alloc_thresh;
> +module_param(indirect_alloc_thresh, uint, S_IRUGO);
> +
> /* FIXME: MTU in config. */
> #define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
> #define GOOD_COPY_LEN 128
> @@ -1132,6 +1135,7 @@ 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;
> + vdev->indirect_alloc_thresh = indirect_alloc_thresh;
>
> err = init_vqs(vi);
> if (err)
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index fce7347..ccf87db 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -38,6 +38,9 @@
> static unsigned int indirect_thresh;
> module_param(indirect_thresh, uint, S_IRUGO);
>
> +static unsigned int indirect_alloc_thresh;
> +module_param(indirect_alloc_thresh, uint, S_IRUGO);
> +
> struct virtio_balloon
> {
> struct virtio_device *vdev;
> @@ -360,6 +363,7 @@ static int virtballoon_probe(struct virtio_device *vdev)
> vb->vdev = vdev;
> vb->need_stats_update = 0;
> vdev->indirect_thresh = indirect_thresh;
> + vdev->indirect_alloc_thresh = indirect_alloc_thresh;
>
> err = init_vqs(vb);
> if (err)
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 99a64a7..e8b9c54 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -93,6 +93,10 @@ struct vring_virtqueue
> */
> unsigned int indirect_thresh;
>
> + /* Buffers below this size will be allocated from cache */
> + unsigned int indirect_alloc_thresh;
> + struct kmem_cache *indirect_cache;
> +
> /* Host publishes avail event idx */
> bool event;
>
> @@ -135,7 +139,10 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
> unsigned head;
> int i;
>
> - desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
> + if ((out + in) <= vq->indirect_alloc_thresh)
> + desc = kmem_cache_alloc(vq->indirect_cache, gfp);
> + else
> + desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
> if (!desc)
> return -ENOMEM;
So this means that drivers need to know how large each
descriptor is to avoid trying to allocate 32Mbyte chunks :)
>
> @@ -384,8 +391,13 @@ static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
> i = head;
>
> /* Free the indirect table */
> - if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
> - kfree(phys_to_virt(vq->vring.desc[i].addr));
> + if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT) {
> + if (vq->vring.desc[i].len > vq->indirect_alloc_thresh)
This looks wrong. indirect_alloc_thresh is in entries but len is in
bytes, isn't it?
> + kfree(phys_to_virt(vq->vring.desc[i].addr));
> + else
> + kmem_cache_free(vq->indirect_cache,
> + phys_to_virt(vq->vring.desc[i].addr));
> + }
>
> while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
> i = vq->vring.desc[i].next;
> @@ -654,14 +666,20 @@ struct virtqueue *vring_new_virtqueue(unsigned int num,
> vq->last_used_idx = 0;
> vq->num_added = 0;
> vq->indirect_thresh = 0;
> + vq->indirect_alloc_thresh = 0;
> + vq->indirect_cache = NULL;
> list_add_tail(&vq->vq.list, &vdev->vqs);
> #ifdef DEBUG
> vq->in_use = false;
> vq->last_add_time_valid = false;
> #endif
>
> - if (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->indirect_alloc_thresh = vdev->indirect_alloc_thresh;
> + if (vq->indirect_alloc_thresh)
> + vq->indirect_cache = KMEM_CACHE(vring_desc[vq->indirect_alloc_thresh],
> 0);
I am not a purist but this line looks way too long.
Also - no need to check cache creation succeeded?
On failure - disable caching?
Also - let's check that values are sane before passing them on?
They come from user after all.
Also - should not threshold be per VQ? E.g. for -net we do not
need the cache for RX unless in legacy big packet mode.
> + }
>
> vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
>
> @@ -685,6 +703,8 @@ EXPORT_SYMBOL_GPL(vring_new_virtqueue);
> void vring_del_virtqueue(struct virtqueue *vq)
> {
> list_del(&vq->list);
> + if (to_vvq(vq)->indirect_cache)
> + kmem_cache_destroy(to_vvq(vq)->indirect_cache);
> kfree(to_vvq(vq));
> }
> EXPORT_SYMBOL_GPL(vring_del_virtqueue);
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 48bc457..3261c02 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -70,6 +70,7 @@ struct virtio_device {
> unsigned long features[1];
> void *priv;
> unsigned int indirect_thresh;
> + unsigned int indirect_alloc_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 fc93962..3044c86 100644
> --- a/net/9p/trans_virtio.c
> +++ b/net/9p/trans_virtio.c
> @@ -55,6 +55,9 @@
> static unsigned int indirect_thresh;
> module_param(indirect_thresh, uint, S_IRUGO);
>
> +static unsigned int indirect_alloc_thresh;
> +module_param(indirect_alloc_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);
> @@ -505,6 +508,8 @@ static int p9_virtio_probe(struct virtio_device *vdev)
>
> /* We expect one virtqueue, for requests. */
> vdev->indirect_thresh = indirect_thresh;
> + vdev->indirect_alloc_thresh = indirect_alloc_thresh;
> +
> chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
> if (IS_ERR(chan->vq)) {
> err = PTR_ERR(chan->vq);
> --
> 1.7.12
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