[dpdk-dev] [PATCH] virtio: use zeroed memory for simple TX header
On Mon, Apr 04, 2016 at 03:57:11PM -0700, Rich Lane wrote: > On Mon, Apr 4, 2016 at 1:05 PM, Yuanhan Liu > wrote: > > On Mon, Apr 04, 2016 at 03:13:37PM +0200, Thomas Monjalon wrote: > > Huawei, Yuanhan, any comment? > > > > 2016-03-31 13:01, Rich Lane: > > >? ? ? ? ? ? ? ? ? ? ? ? ? ? ?vq->vq_ring.desc[i + mid_idx].next = i; > > >? ? ? ? ? ? ? ? ? ? ? ? ? ? ?vq->vq_ring.desc[i + mid_idx].addr = > > > -? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?vq->virtio_net_hdr_mem + > > > -? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?i * > vq->hw->vtnet_hdr_size; > > > +? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?vq->virtio_net_hdr_mem; > > I could be wrong, but this looks like a special case when i == 0, > which is by no way that zeroed memory is guaranteed? Huawei, do > you have time to check this patch?? > > > This bug exists because the type of the objects pointed to by > virtio_net_hdr_mem changed in 6dc5de3a (virtio: use indirect ring elements), > but because it isn't a C pointer the compiler didn't?catch the type mismatch. > We could also fix it with: > > ? ? vq->virtio_net_hdr_mem + i * sizeof(struct virtio_tx_region) + offsetof > (struct virtio_tx_region, tx_hdr) > > Given that tx_hdr is the first member in struct virtio_tx_region, and using a > single header optimizes cache use, that simplifies to the code in my patch. It does. However, it hurts readability. > The > virtio-net header is never written to by simple TX so it remains zeroed. > > I can respin the patch using offsetof if that's preferred. Yes, please. In such way, we could also align with the setting up code at virtio_dev_queue_setup(). BTW, I have one question: will simple Tx work with indirect buf enabled? > Note that right now virtio simple TX is broken with DPDK vhost due to the > flood > of error messages. Yes, we need the fix, and thanks for the catching. BTW, it's a regression fix, you'd better add a Fixline into your commit log. --yliu
[dpdk-dev] [PATCH] virtio: use zeroed memory for simple TX header
On Mon, Apr 04, 2016 at 03:13:37PM +0200, Thomas Monjalon wrote: > Huawei, Yuanhan, any comment? > > 2016-03-31 13:01, Rich Lane: > > vq->vq_ring.desc[i + mid_idx].next = i; > > vq->vq_ring.desc[i + mid_idx].addr = > > - vq->virtio_net_hdr_mem + > > - i * vq->hw->vtnet_hdr_size; > > + vq->virtio_net_hdr_mem; I could be wrong, but this looks like a special case when i == 0, which is by no way that zeroed memory is guaranteed? Huawei, do you have time to check this patch? Thanks.
[dpdk-dev] [PATCH] virtio: use zeroed memory for simple TX header
On Mon, Apr 4, 2016 at 1:05 PM, Yuanhan Liu wrote: > On Mon, Apr 04, 2016 at 03:13:37PM +0200, Thomas Monjalon wrote: > > Huawei, Yuanhan, any comment? > > > > 2016-03-31 13:01, Rich Lane: > > > vq->vq_ring.desc[i + mid_idx].next = i; > > > vq->vq_ring.desc[i + mid_idx].addr = > > > - vq->virtio_net_hdr_mem + > > > - i * vq->hw->vtnet_hdr_size; > > > + vq->virtio_net_hdr_mem; > > I could be wrong, but this looks like a special case when i == 0, > which is by no way that zeroed memory is guaranteed? Huawei, do > you have time to check this patch? This bug exists because the type of the objects pointed to by virtio_net_hdr_mem changed in 6dc5de3a (virtio: use indirect ring elements), but because it isn't a C pointer the compiler didn't catch the type mismatch. We could also fix it with: vq->virtio_net_hdr_mem + i * sizeof(struct virtio_tx_region) + offsetof(struct virtio_tx_region, tx_hdr) Given that tx_hdr is the first member in struct virtio_tx_region, and using a single header optimizes cache use, that simplifies to the code in my patch. The virtio-net header is never written to by simple TX so it remains zeroed. I can respin the patch using offsetof if that's preferred. Note that right now virtio simple TX is broken with DPDK vhost due to the flood of error messages.
[dpdk-dev] [PATCH] virtio: use zeroed memory for simple TX header
Huawei, Yuanhan, any comment? 2016-03-31 13:01, Rich Lane: > vq->vq_ring.desc[i + mid_idx].next = i; > vq->vq_ring.desc[i + mid_idx].addr = > - vq->virtio_net_hdr_mem + > - i * vq->hw->vtnet_hdr_size; > + vq->virtio_net_hdr_mem; > vq->vq_ring.desc[i + mid_idx].len = > vq->hw->vtnet_hdr_size;
[dpdk-dev] [PATCH] virtio: use zeroed memory for simple TX header
For simple TX the virtio-net header must be zeroed, but it was using memory that had been initialized with indirect descriptor tables. This resulted in "unsupported gso type" errors from librte_vhost. We can use the same memory for every descriptor to save cachelines in the vswitch. Signed-off-by: Rich Lane --- drivers/net/virtio/virtio_rxtx.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c index 2b88efd..1df2df6 100644 --- a/drivers/net/virtio/virtio_rxtx.c +++ b/drivers/net/virtio/virtio_rxtx.c @@ -376,8 +376,7 @@ virtio_dev_vring_start(struct virtqueue *vq, int queue_type) vq->vq_ring.avail->ring[i] = i + mid_idx; vq->vq_ring.desc[i + mid_idx].next = i; vq->vq_ring.desc[i + mid_idx].addr = - vq->virtio_net_hdr_mem + - i * vq->hw->vtnet_hdr_size; + vq->virtio_net_hdr_mem; vq->vq_ring.desc[i + mid_idx].len = vq->hw->vtnet_hdr_size; vq->vq_ring.desc[i + mid_idx].flags = -- 1.9.1
