From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= Subject: [PATCH v4 3/7] vhost: batching fetches Date: Wed, 1 Apr 2020 20:31:14 +0200 Message-ID: <20200401183118.8334-4-eperezma@redhat.com> References: <20200401183118.8334-1-eperezma@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20200401183118.8334-1-eperezma@redhat.com> Sender: kvm-owner@vger.kernel.org To: "Michael S. Tsirkin" Cc: "virtualization@lists.linux-foundation.org" , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Linux Next Mailing List , Stephen Rothwell , kvm list , Halil Pasic , "linux-kernel@vger.kernel.org" , Cornelia Huck , Christian Borntraeger List-Id: virtualization@lists.linuxfoundation.org From: "Michael S. Tsirkin" With this patch applied, new and old code perform identically. Lots of extra optimizations are now possible, e.g. we can fetch multiple heads with copy_from/to_user now. We can get rid of maintaining the log array. Etc etc. Signed-off-by: Michael S. Tsirkin Signed-off-by: Eugenio P=C3=A9rez --- drivers/vhost/test.c | 2 +- drivers/vhost/vhost.c | 47 ++++++++++++++++++++++++++++++++++++++----- drivers/vhost/vhost.h | 5 ++++- 3 files changed, 47 insertions(+), 7 deletions(-) diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c index 9a3a09005e03..02806d6f84ef 100644 --- a/drivers/vhost/test.c +++ b/drivers/vhost/test.c @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struc= t file *f) dev =3D &n->dev; vqs[VHOST_TEST_VQ] =3D &n->vqs[VHOST_TEST_VQ]; n->vqs[VHOST_TEST_VQ].handle_kick =3D handle_vq_kick; - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV, + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64, VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, NULL); =20 f->private_data =3D n; diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 6ca658c21e15..0395229486a9 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -299,6 +299,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, { vq->num =3D 1; vq->ndescs =3D 0; + vq->first_desc =3D 0; vq->desc =3D NULL; vq->avail =3D NULL; vq->used =3D NULL; @@ -367,6 +368,11 @@ static int vhost_worker(void *data) return 0; } =20 +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq) +{ + return vq->max_descs - UIO_MAXIOV; +} + static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq) { kfree(vq->descs); @@ -389,6 +395,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *= dev) for (i =3D 0; i < dev->nvqs; ++i) { vq =3D dev->vqs[i]; vq->max_descs =3D dev->iov_limit; + if (vhost_vq_num_batch_descs(vq) < 0) { + return -EINVAL; + } vq->descs =3D kmalloc_array(vq->max_descs, sizeof(*vq->descs), GFP_KERNEL); @@ -1570,6 +1579,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigne= d int ioctl, void __user *arg vq->last_avail_idx =3D s.num; /* Forget the cached index value. */ vq->avail_idx =3D vq->last_avail_idx; + vq->ndescs =3D vq->first_desc =3D 0; break; case VHOST_GET_VRING_BASE: s.index =3D idx; @@ -2136,7 +2146,7 @@ static int fetch_indirect_descs(struct vhost_virtqu= eue *vq, return 0; } =20 -static int fetch_descs(struct vhost_virtqueue *vq) +static int fetch_buf(struct vhost_virtqueue *vq) { unsigned int i, head, found =3D 0; struct vhost_desc *last; @@ -2149,7 +2159,11 @@ static int fetch_descs(struct vhost_virtqueue *vq) /* Check it isn't doing very strange things with descriptor numbers. */ last_avail_idx =3D vq->last_avail_idx; =20 - if (vq->avail_idx =3D=3D vq->last_avail_idx) { + if (unlikely(vq->avail_idx =3D=3D vq->last_avail_idx)) { + /* If we already have work to do, don't bother re-checking. */ + if (likely(vq->ndescs)) + return vq->num; + if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { vq_err(vq, "Failed to access avail idx at %p\n", &vq->avail->idx); @@ -2240,6 +2254,24 @@ static int fetch_descs(struct vhost_virtqueue *vq) return 0; } =20 +static int fetch_descs(struct vhost_virtqueue *vq) +{ + int ret =3D 0; + + if (unlikely(vq->first_desc >=3D vq->ndescs)) { + vq->first_desc =3D 0; + vq->ndescs =3D 0; + } + + if (vq->ndescs) + return 0; + + while (!ret && vq->ndescs <=3D vhost_vq_num_batch_descs(vq)) + ret =3D fetch_buf(vq); + + return vq->ndescs ? 0 : ret; +} + /* This looks in the virtqueue and for the first available buffer, and c= onverts * it to an iovec for convenient access. Since descriptors consist of s= ome * number of output then some number of input descriptors, it's actually= two @@ -2265,7 +2297,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, if (unlikely(log)) *log_num =3D 0; =20 - for (i =3D 0; i < vq->ndescs; ++i) { + for (i =3D vq->first_desc; i < vq->ndescs; ++i) { unsigned iov_count =3D *in_num + *out_num; struct vhost_desc *desc =3D &vq->descs[i]; int access; @@ -2311,14 +2343,19 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, } =20 ret =3D desc->id; + + if (!(desc->flags & VRING_DESC_F_NEXT)) + break; } =20 - vq->ndescs =3D 0; + vq->first_desc =3D i + 1; =20 return ret; =20 err: - vhost_discard_vq_desc(vq, 1); + for (i =3D vq->first_desc; i < vq->ndescs; ++i) + if (!(vq->descs[i].flags & VRING_DESC_F_NEXT)) + vhost_discard_vq_desc(vq, 1); vq->ndescs =3D 0; =20 return ret; diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index e5f295e5ffcc..cc82918158d2 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -81,6 +81,7 @@ struct vhost_virtqueue { =20 struct vhost_desc *descs; int ndescs; + int first_desc; int max_descs; =20 struct file *kick; @@ -229,7 +230,7 @@ void vhost_iotlb_map_free(struct vhost_iotlb *iotlb, struct vhost_iotlb_map *map); =20 #define vq_err(vq, fmt, ...) do { \ - pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \ + pr_err(pr_fmt(fmt), ##__VA_ARGS__); \ if ((vq)->error_ctx) \ eventfd_signal((vq)->error_ctx, 1);\ } while (0) @@ -255,6 +256,8 @@ static inline void vhost_vq_set_backend(struct vhost_= virtqueue *vq, void *private_data) { vq->private_data =3D private_data; + vq->ndescs =3D 0; + vq->first_desc =3D 0; } =20 /** --=20 2.18.1