[PATCH v2] vhost: add support for large buffers.
There is a warning reported by devtools/check-git-log.sh The '.' at the end of the title should be dropped. On Fri, Oct 04, 2019 at 05:10:08PM -0300, Flavio Leitner wrote: > The rte_vhost_dequeue_burst supports two ways of dequeuing data. > If the data fits into a buffer, then all data is copied and a > single linear buffer is returned. Otherwise it allocates > additional mbufs and chains them together to return a multiple > segments mbuf. > > While that covers most use cases, it forces applications that > need to work with larger data sizes to support multiple segments > mbufs. The non-linear characteristic brings complexity and > performance implications to the application. > > To resolve the issue, let the host provide during registration > if attaching an external buffer to pktmbuf is supported and if > only linear buffer are supported. > > Signed-off-by: Flavio Leitner <f...@sysclose.org> > --- > doc/guides/prog_guide/vhost_lib.rst | 35 ++++++++++ > lib/librte_vhost/rte_vhost.h | 4 ++ > lib/librte_vhost/socket.c | 10 +++ > lib/librte_vhost/vhost.c | 22 ++++++ > lib/librte_vhost/vhost.h | 4 ++ > lib/librte_vhost/virtio_net.c | 103 ++++++++++++++++++++++++++-- > 6 files changed, 172 insertions(+), 6 deletions(-) > > - Changelog: > V2: > - Used rte_malloc() instead of another mempool as suggested by Shahaf. > - Added the documentation section. > - Using driver registration to negotiate the features. > - OvS PoC code: > > https://github.com/fleitner/ovs/commit/8fc197c40b1d4fda331686a7b919e9e2b670dda7 > > diff --git a/doc/guides/prog_guide/vhost_lib.rst > b/doc/guides/prog_guide/vhost_lib.rst > index fc3ee4353..07e40e3c5 100644 > --- a/doc/guides/prog_guide/vhost_lib.rst > +++ b/doc/guides/prog_guide/vhost_lib.rst > @@ -117,6 +117,41 @@ The following is an overview of some key Vhost API > functions: > Enabling this flag should only be done when the calling application does > not pre-fault the guest shared memory, otherwise migration would fail. > > + - ``RTE_VHOST_USER_LINEARBUF_SUPPORT`` > + > + Enabling this flag forces vhost dequeue function to only provide linear > + pktmbuf (no multi-segmented pktmbuf). > + > + The vhost library by default provides a single pktmbuf for given a > + packet, but if for some reason the data doesn't fit into a single > + pktmbuf (e.g., TSO is enabled), the library will allocate additional > + pktmbufs from the same mempool and chain them together to create a > + multi-segmented pktmbuf. > + > + However, the vhost application needs to support multi-segmented format. > + If the vhost application does not support that format and requires large > + buffers to be dequeue, this flag should be enabled to force only linear > + buffers (see RTE_VHOST_USER_EXTBUF_SUPPORT) or drop the packet. > + > + It is disabled by default. > + > + - ``RTE_VHOST_USER_EXTBUF_SUPPORT`` > + > + Enabling this flag allows vhost dequeue function to allocate and attach > + an external buffer to a pktmbuf if the pkmbuf doesn't provide enough > + space to store all data. > + > + This is useful when the vhost application wants to support large packets > + but doesn't want to increase the default mempool object size nor to > + support multi-segmented mbufs (non-linear). In this case, a fresh buffer > + is allocated using rte_malloc() which gets attached to a pktmbuf using > + rte_pktmbuf_attach_extbuf(). > + > + See RTE_VHOST_USER_LINEARBUF_SUPPORT as well to disable multi-segmented > + mbufs for application that doesn't support chained mbufs. > + > + It is disabled by default. > + > * ``rte_vhost_driver_set_features(path, features)`` > > This function sets the feature bits the vhost-user driver supports. The > diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h > index 19474bca0..b821b5df4 100644 > --- a/lib/librte_vhost/rte_vhost.h > +++ b/lib/librte_vhost/rte_vhost.h > @@ -30,6 +30,10 @@ extern "C" { > #define RTE_VHOST_USER_DEQUEUE_ZERO_COPY (1ULL << 2) > #define RTE_VHOST_USER_IOMMU_SUPPORT (1ULL << 3) > #define RTE_VHOST_USER_POSTCOPY_SUPPORT (1ULL << 4) > +/* support mbuf with external buffer attached */ > +#define RTE_VHOST_USER_EXTBUF_SUPPORT (1ULL << 5) > +/* support only linear buffers (no chained mbufs) */ > +#define RTE_VHOST_USER_LINEARBUF_SUPPORT (1ULL << 6) > > /** Protocol features. */ > #ifndef VHOST_USER_PROTOCOL_F_MQ > diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c > index 274988c4d..0ba610fda 100644 > --- a/lib/librte_vhost/socket.c > +++ b/lib/librte_vhost/socket.c > @@ -40,6 +40,8 @@ struct vhost_user_socket { > bool dequeue_zero_copy; > bool iommu_support; > bool use_builtin_virtio_net; > + bool extbuf; > + bool linearbuf; > > /* > * The "supported_features" indicates the feature bits the > @@ -232,6 +234,12 @@ vhost_user_add_connection(int fd, struct > vhost_user_socket *vsocket) > if (vsocket->dequeue_zero_copy) > vhost_enable_dequeue_zero_copy(vid); > > + if (vsocket->extbuf) > + vhost_enable_extbuf(vid); > + > + if (vsocket->linearbuf) > + vhost_enable_linearbuf(vid); > + > RTE_LOG(INFO, VHOST_CONFIG, "new device, handle is %d\n", vid); > > if (vsocket->notify_ops->new_connection) { > @@ -870,6 +878,8 @@ rte_vhost_driver_register(const char *path, uint64_t > flags) > goto out_free; > } > vsocket->dequeue_zero_copy = flags & RTE_VHOST_USER_DEQUEUE_ZERO_COPY; > + vsocket->extbuf = flags & RTE_VHOST_USER_EXTBUF_SUPPORT; > + vsocket->linearbuf = flags & RTE_VHOST_USER_LINEARBUF_SUPPORT; It could be problematic to use dequeue_zero_copy with above two features at the same time. We may want to reject such combination. > > /* > * Set the supported features correctly for the builtin vhost-user > diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c > index cea44df8c..77457f538 100644 > --- a/lib/librte_vhost/vhost.c > +++ b/lib/librte_vhost/vhost.c > @@ -605,6 +605,28 @@ vhost_set_builtin_virtio_net(int vid, bool enable) > dev->flags &= ~VIRTIO_DEV_BUILTIN_VIRTIO_NET; > } > > +void > +vhost_enable_extbuf(int vid) > +{ > + struct virtio_net *dev = get_device(vid); > + > + if (dev == NULL) > + return; > + > + dev->extbuf = 1; > +} > + > +void > +vhost_enable_linearbuf(int vid) > +{ > + struct virtio_net *dev = get_device(vid); > + > + if (dev == NULL) > + return; > + > + dev->linearbuf = 1; > +} > + > int > rte_vhost_get_mtu(int vid, uint16_t *mtu) > { > diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h > index 5131a97a3..0346bd118 100644 > --- a/lib/librte_vhost/vhost.h > +++ b/lib/librte_vhost/vhost.h > @@ -302,6 +302,8 @@ struct virtio_net { > rte_atomic16_t broadcast_rarp; > uint32_t nr_vring; > int dequeue_zero_copy; > + int extbuf; > + int linearbuf; > struct vhost_virtqueue *virtqueue[VHOST_MAX_QUEUE_PAIRS * 2]; > #define IF_NAME_SZ (PATH_MAX > IFNAMSIZ ? PATH_MAX : IFNAMSIZ) > char ifname[IF_NAME_SZ]; > @@ -476,6 +478,8 @@ void vhost_attach_vdpa_device(int vid, int did); > void vhost_set_ifname(int, const char *if_name, unsigned int if_len); > void vhost_enable_dequeue_zero_copy(int vid); > void vhost_set_builtin_virtio_net(int vid, bool enable); > +void vhost_enable_extbuf(int vid); > +void vhost_enable_linearbuf(int vid); > > struct vhost_device_ops const *vhost_driver_callback_get(const char *path); > > diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c > index 5b85b832d..fca75161d 100644 > --- a/lib/librte_vhost/virtio_net.c > +++ b/lib/librte_vhost/virtio_net.c > @@ -2,6 +2,7 @@ > * Copyright(c) 2010-2016 Intel Corporation > */ > > +#include <assert.h> > #include <stdint.h> > #include <stdbool.h> > #include <linux/virtio_net.h> > @@ -1289,6 +1290,96 @@ get_zmbuf(struct vhost_virtqueue *vq) > return NULL; > } > > +static void > +virtio_dev_extbuf_free(void *addr __rte_unused, void *opaque) > +{ > + rte_free(opaque); > +} > + > +static int > +virtio_dev_extbuf_alloc(struct rte_mbuf *pkt, uint16_t size) > +{ > + struct rte_mbuf_ext_shared_info *shinfo; > + uint16_t buf_len; It also includes RTE_PKTMBUF_HEADROOM and sizeof(*shinfo). Is uint16_t big enough? > + rte_iova_t iova; > + void *buf; > + > + shinfo = NULL; > + buf_len = size + RTE_PKTMBUF_HEADROOM; > + > + /* Try to use pkt buffer to store shinfo to reduce the amount of memory > + * required, otherwise store shinfo in the new buffer. > + */ > + if (rte_pktmbuf_tailroom(pkt) > sizeof(*shinfo)) > + shinfo = rte_pktmbuf_mtod(pkt, > + struct rte_mbuf_ext_shared_info *); > + else { > + if (unlikely(buf_len + sizeof(shinfo) > UINT16_MAX)) { Should be sizeof(*shinfo) > + RTE_LOG(ERR, VHOST_DATA, > + "buffer size exceeded maximum.\n"); > + return -ENOSPC; > + } > + > + buf_len += sizeof(shinfo); Ditto. > + } > + > + buf = rte_malloc(NULL, buf_len, RTE_CACHE_LINE_SIZE); > + if (unlikely(buf == NULL)) { > + RTE_LOG(ERR, VHOST_DATA, > + "Failed to allocate memory for mbuf.\n"); Looks better to just have 3 tabs before the string. > + return -ENOMEM; > + } > + > + /* initialize shinfo */ > + if (shinfo) { > + shinfo->free_cb = virtio_dev_extbuf_free; > + shinfo->fcb_opaque = buf; > + rte_mbuf_ext_refcnt_set(shinfo, 1); > + } else { > + shinfo = rte_pktmbuf_ext_shinfo_init_helper(buf, &buf_len, > + virtio_dev_extbuf_free, buf); > + assert(shinfo); As a library, we shouldn't abort the process. We can just return the error. > + } > + > + iova = rte_mempool_virt2iova(buf); Should be rte_malloc_virt2iova(). > + rte_pktmbuf_attach_extbuf(pkt, buf, iova, buf_len, shinfo); > + rte_pktmbuf_reset_headroom(pkt); > + assert(pkt->ol_flags == EXT_ATTACHED_MBUF); Ditto. > + > + return 0; > +} > + > +/* > + * Allocate a host supported pktmbuf. > + */ > +static __rte_always_inline struct rte_mbuf * > +virtio_dev_pktmbuf_alloc(struct virtio_net *dev, struct rte_mempool *mp, > + uint16_t data_len) > +{ > + struct rte_mbuf *pkt = rte_pktmbuf_alloc(mp); > + > + if (unlikely(pkt == NULL)) > + return NULL; > + > + if (rte_pktmbuf_tailroom(pkt) >= data_len) > + return pkt; > + > + /* attach an external buffer if supported */ > + if (dev->extbuf && !virtio_dev_extbuf_alloc(pkt, data_len)) > + return pkt; > + > + /* check if chained buffers are allowed */ > + if (!dev->linearbuf) > + return pkt; > + > + /* Data doesn't fit into the buffer and the host supports > + * only linear buffers > + */ > + rte_pktmbuf_free(pkt); > + > + return NULL; > +} > + > static __rte_noinline uint16_t > virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq, > struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count) > @@ -1343,21 +1434,21 @@ virtio_dev_tx_split(struct virtio_net *dev, struct > vhost_virtqueue *vq, > for (i = 0; i < count; i++) { > struct buf_vector buf_vec[BUF_VECTOR_MAX]; > uint16_t head_idx; > - uint32_t dummy_len; > + uint32_t buf_len; > uint16_t nr_vec = 0; > int err; > > if (unlikely(fill_vec_buf_split(dev, vq, > vq->last_avail_idx + i, > &nr_vec, buf_vec, > - &head_idx, &dummy_len, > + &head_idx, &buf_len, > VHOST_ACCESS_RO) < 0)) > break; > > if (likely(dev->dequeue_zero_copy == 0)) > update_shadow_used_ring_split(vq, head_idx, 0); > > - pkts[i] = rte_pktmbuf_alloc(mbuf_pool); > + pkts[i] = virtio_dev_pktmbuf_alloc(dev, mbuf_pool, buf_len); > if (unlikely(pkts[i] == NULL)) { > RTE_LOG(ERR, VHOST_DATA, > "Failed to allocate memory for mbuf.\n"); > @@ -1451,14 +1542,14 @@ virtio_dev_tx_packed(struct virtio_net *dev, struct > vhost_virtqueue *vq, > for (i = 0; i < count; i++) { > struct buf_vector buf_vec[BUF_VECTOR_MAX]; > uint16_t buf_id; > - uint32_t dummy_len; > + uint32_t buf_len; > uint16_t desc_count, nr_vec = 0; > int err; > > if (unlikely(fill_vec_buf_packed(dev, vq, > vq->last_avail_idx, &desc_count, > buf_vec, &nr_vec, > - &buf_id, &dummy_len, > + &buf_id, &buf_len, > VHOST_ACCESS_RO) < 0)) > break; > > @@ -1466,7 +1557,7 @@ virtio_dev_tx_packed(struct virtio_net *dev, struct > vhost_virtqueue *vq, > update_shadow_used_ring_packed(vq, buf_id, 0, > desc_count); > > - pkts[i] = rte_pktmbuf_alloc(mbuf_pool); > + pkts[i] = virtio_dev_pktmbuf_alloc(dev, mbuf_pool, buf_len); > if (unlikely(pkts[i] == NULL)) { > RTE_LOG(ERR, VHOST_DATA, > "Failed to allocate memory for mbuf.\n"); > -- > 2.20.1 >
