On Wed, Aug 29, 2012 at 07:14:01PM +0200, Sasha Levin wrote: > On 08/29/2012 05:38 PM, Michael S. Tsirkin wrote: > > 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 <levinsasha...@gmail.com> > > > > The API is ugly - how does driver know what to set? > > Is this a typical request size? Then let's call it that. > > We've discussed it during the RFC phase, the idea is that we don't know what > would be a good number to use as threshold - which is why I'd like to keep it > disabled as default until it gets more serious tests. > > The driver doesn't know what to set, the plan was to make it a dynamic > algorithms which would change it based on current load. Since I can't really > do > testing which will provide the correct values for that, the decision was to do > it this way as the first stage and modify it later. > > > Also this is really per VQ, right? > > Right, we keep it per-device at this stage to keep it simple. > > > What is a good default for net? I guess max sg? > > I think that it depends on the workload. I'd say we should keep the default > to 0 > (disabled) unless we can have a good way to adjust it to the load.
For *all* drivers? Then it is mostly useless. No one has the time to tweak module parameters in real life. For virtio-net, 16+1 is not too much and ensures we always use the cache. If that works better than 0 I would say run with 17. > >> --- > >> > >> 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 :) > > Right, this interface isn't perfect and would hopefully be removed in favour > of > a dynamic algorithm in the driver. > > >> > >> @@ -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? > > Uh, yes. It's supposed to be '.len/sizeof(struct vring_desc)'. > > >> + 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. > > will fix these two. > > > 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. > > We've discussed it two months ago over IRC (at least thats what I have in my > notes) - the plan was to keep it simple per-device until something more > advanced > to deal with the threshold shows up. > > > Thanks, > Sasha > > > > >> + } > >> > >> 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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html