similar to: [PATCHv2 RFC 0/4] virtio and vhost-net capacity handling

OK, here's a new attempt to use the new capacity api. I also added more comments to clarify the logic. Hope this is more readable. Let me know pls. This is on top of the patches applied by Rusty. Note: there are now actually 2 calls to fee_old_xmit_skbs on data path so instead of passing flag '2' to the second one I thought we can just make each call free up at least 1 skb. This

OK, here's a new attempt to use the new capacity api. I also added more comments to clarify the logic. Hope this is more readable. Let me know pls. This is on top of the patches applied by Rusty. Note: there are now actually 2 calls to fee_old_xmit_skbs on data path so instead of passing flag '2' to the second one I thought we can just make each call free up at least 1 skb. This

OK, here's a large patchset that implements the virtio spec update that I sent earlier. It supercedes the PUBLISH_USED_IDX patches I sent out earlier. I know it's a lot to ask but please test, and please consider for 2.6.40 :) I see nice performance improvements: one run showed going from 12 to 18 Gbit/s host to guest with netperf, but I did not spend a lot of time testing performance,

OK, here's a large patchset that implements the virtio spec update that I sent earlier. It supercedes the PUBLISH_USED_IDX patches I sent out earlier. I know it's a lot to ask but please test, and please consider for 2.6.40 :) I see nice performance improvements: one run showed going from 12 to 18 Gbit/s host to guest with netperf, but I did not spend a lot of time testing performance,

OK, here is the large patchset that implements the virtio spec update that I sent earlier (the spec itself needs a minor update, will send that out too next week, but I think we are on the same page here already). It supercedes the PUBLISH_USED_IDX patches I sent out earlier. What will follow will be a patchset that actually includes 4 sets of patches. I note below their status. Please consider

OK, here is the large patchset that implements the virtio spec update that I sent earlier (the spec itself needs a minor update, will send that out too next week, but I think we are on the same page here already). It supercedes the PUBLISH_USED_IDX patches I sent out earlier. What will follow will be a patchset that actually includes 4 sets of patches. I note below their status. Please consider

From: Mark McLoughlin <markmc at redhat.com> hdr->csum_start is the offset from the start of the ethernet header to the transport layer checksum field. skb->csum_start is the offset from skb->head. skb_partial_csum_set() assumes that skb->data points to the ethernet header - i.e. it computes skb->csum_start by adding the headroom to hdr->csum_start. Since

On Thursday 01 May 2008 00:31:46 Mark McLoughlin wrote: > virtio_net currently only frees old transmit skbs just > before queueing new ones. If the queue is full, it then > enables interrupts and waits for notification that more > work has been performed. Hi Mark, This patch is fine, but it's better to do it from skb_xmit_done(). Of course, this is usually called from an

On Thursday 01 May 2008 00:31:46 Mark McLoughlin wrote: > virtio_net currently only frees old transmit skbs just > before queueing new ones. If the queue is full, it then > enables interrupts and waits for notification that more > work has been performed. Hi Mark, This patch is fine, but it's better to do it from skb_xmit_done(). Of course, this is usually called from an

virtio net used to unlink skbs from send queues on error, but ever since 48925e372f04f5e35fec6269127c62b2c71ab794 we do not do this. This causes guest data corruption and crashes with vhost since net core can requeue the skb or free it without it being taken off the list. This patch fixes this by queueing the skb after successfull transmit. Signed-off-by: Michael S. Tsirkin <mst at

virtio net used to unlink skbs from send queues on error, but ever since 48925e372f04f5e35fec6269127c62b2c71ab794 we do not do this. This causes guest data corruption and crashes with vhost since net core can requeue the skb or free it without it being taken off the list. This patch fixes this by queueing the skb after successfull transmit. Signed-off-by: Michael S. Tsirkin <mst at

If we fail to transmit a packet, we assume the queue is full and put the skb into last_xmit_skb. However, if more space frees up before we xmit it, we loop, and the result can be transmitting the same skb twice. Fix is simple: set skb to NULL if we've used it in some way, and check before sending. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c |

If we fail to transmit a packet, we assume the queue is full and put the skb into last_xmit_skb. However, if more space frees up before we xmit it, we loop, and the result can be transmitting the same skb twice. Fix is simple: set skb to NULL if we've used it in some way, and check before sending. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c |

virtio net will never try to overflow the TX ring, so the only reason add_buf may fail is out of memory. Thus, we can not stop the device until some request completes - there's no guarantee anything at all is outstanding. Make the error message clearer as well: error here does not indicate queue full. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/net/virtio_net.c |

virtio net will never try to overflow the TX ring, so the only reason add_buf may fail is out of memory. Thus, we can not stop the device until some request completes - there's no guarantee anything at all is outstanding. Make the error message clearer as well: error here does not indicate queue full. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/net/virtio_net.c |

virtqueue ops were introduced in the hope that we'll have multiple implementations besides virtio_ring, but none have surfaced so far, and given that existing virtio ring is deployed in production we are likely stuck with it now, so this layer just adds complexity and overhead. Further, the need to pass vq twice to each call (as in dev->vq->vq_ops->kick(dev->vq) ) adds potential

virtqueue ops were introduced in the hope that we'll have multiple implementations besides virtio_ring, but none have surfaced so far, and given that existing virtio ring is deployed in production we are likely stuck with it now, so this layer just adds complexity and overhead. Further, the need to pass vq twice to each call (as in dev->vq->vq_ops->kick(dev->vq) ) adds potential

Thinking about Sasha's patches, we can reduce ring usage for virtio net small packets dramatically if we put virtio net header inline with the data. This can be done for free in case guest net stack allocated extra head room for the packet, and I don't see why would this have any downsides. Even though with my recent patches qemu no longer requires header to be the first s/g element, we

Thinking about Sasha's patches, we can reduce ring usage for virtio net small packets dramatically if we put virtio net header inline with the data. This can be done for free in case guest net stack allocated extra head room for the packet, and I don't see why would this have any downsides. Even though with my recent patches qemu no longer requires header to be the first s/g element, we

skb is only NULL the first time around: it's more correct to test for being under-budget. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> diff -r 2a94425ac7d5 drivers/net/virtio_net.c --- a/drivers/net/virtio_net.c Thu Nov 15 13:47:28 2007 +1100 +++ b/drivers/net/virtio_net.c Thu Nov 15 23:10:44 2007 +1100 @@ -198,8 +198,8 @@ again: if (vi->num < vi->max / 2)