similar to: [PATCH RFC] virtio_net: fix patch: virtio_net: limit xmit polling

The virtio_net driver is complicated by the two methods of freeing old xmit buffers (in addition to freeing old ones at the start of the xmit path). The original code used a 1/10 second timer attached to xmit_free(), reset on every xmit. Before we orphaned skbs on xmit, the transmitting userspace could block with a full socket until the timer fired, the skb destructor was called, and they were

The virtio_net driver is complicated by the two methods of freeing old xmit buffers (in addition to freeing old ones at the start of the xmit path). The original code used a 1/10 second timer attached to xmit_free(), reset on every xmit. Before we orphaned skbs on xmit, the transmitting userspace could block with a full socket until the timer fired, the skb destructor was called, and they were

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 |

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. Warning: untested. Posting now to give people chance to comment on the API. Changes from v1: - fix comment in patch 2 to correct confusion noted by Rusty - rewrite patch 3 along the lines

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. Warning: untested. Posting now to give people chance to comment on the API. Changes from v1: - fix comment in patch 2 to correct confusion noted by Rusty - rewrite patch 3 along the lines

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

This effectively reverts 99ffc696d10b28580fe93441d627cf290ac4484c "virtio: wean net driver off NETDEV_TX_BUSY". The complexity of queuing an skb (setting a tasklet to re-xmit) is questionable, especially once we get rid of the other reason for the tasklet in the next patch. If the skb won't fit in the tx queue, just return NETDEV_TX_BUSY. It might be frowned upon, but it's

This effectively reverts 99ffc696d10b28580fe93441d627cf290ac4484c "virtio: wean net driver off NETDEV_TX_BUSY". The complexity of queuing an skb (setting a tasklet to re-xmit) is questionable, especially once we get rid of the other reason for the tasklet in the next patch. If the skb won't fit in the tx queue, just return NETDEV_TX_BUSY. It might be frowned upon, but it's

OK, different people seem to test different trees. In the hope to get everyone on the same page, I created several variants of this patch so they can be compared. Whoever's interested, please check out the following, and tell me how these compare: kernel: git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git virtio-net-limit-xmit-polling/base - this is net-next baseline to test

OK, different people seem to test different trees. In the hope to get everyone on the same page, I created several variants of this patch so they can be compared. Whoever's interested, please check out the following, and tell me how these compare: kernel: git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git virtio-net-limit-xmit-polling/base - this is net-next baseline to test

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,

Herbert tells me that returning NETDEV_TX_BUSY from hard_start_xmit is seen as a poor thing to do; we should cache the packet and stop the queue. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c | 57 +++++++++++++++++++++++++++++++---------------- 1 file changed, 38 insertions(+), 19 deletions(-) diff -r a936d320f6d5 drivers/net/virtio_net.c ---

Herbert tells me that returning NETDEV_TX_BUSY from hard_start_xmit is seen as a poor thing to do; we should cache the packet and stop the queue. Signed-off-by: Rusty Russell <rusty at rustcorp.com.au> --- drivers/net/virtio_net.c | 57 +++++++++++++++++++++++++++++++---------------- 1 file changed, 38 insertions(+), 19 deletions(-) diff -r a936d320f6d5 drivers/net/virtio_net.c ---

MSIX spec requires that device can be operated with all vectors masked, by polling. So the following patchset (lightly tested) adds this ability: when driver reads ISR, the device recalls a pending notification, and returns pending status in the ISR register. The polling driver can operate as follows: - map all VQs and config to the same vector - poll ISR to get status - this also flushes VQ

MSIX spec requires that device can be operated with all vectors masked, by polling. So the following patchset (lightly tested) adds this ability: when driver reads ISR, the device recalls a pending notification, and returns pending status in the ISR register. The polling driver can operate as follows: - map all VQs and config to the same vector - poll ISR to get status - this also flushes VQ