similar to: TODO list for qemu+KVM networking performance v2

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

(Note the arch/s390 bit is from virtio console on KVM/s390) The following changes since commit 0988c37c248e824953d95a11412696c348dbca91: Linus Torvalds (1): Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/.../tip/linux-2.6-tip are available in the git repository at: ssh://master.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus.git master Andrew

(Note the arch/s390 bit is from virtio console on KVM/s390) The following changes since commit 0988c37c248e824953d95a11412696c348dbca91: Linus Torvalds (1): Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/.../tip/linux-2.6-tip are available in the git repository at: ssh://master.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus.git master Andrew

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

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

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

Since we want to reset the device to remove them, this is simpler (device is reset for us on driver remove). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> --- drivers/net/virtio_net.c | 44 +++++++++++++++++++++++++------------------- 1 file changed, 25 insertions(+), 19 deletions(-) diff -r 7e5b3ff06f60 drivers/net/virtio_net.c --- a/drivers/net/virtio_net.c Wed Jan 23 22:53:14

Since we want to reset the device to remove them, this is simpler (device is reset for us on driver remove). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> --- drivers/net/virtio_net.c | 44 +++++++++++++++++++++++++------------------- 1 file changed, 25 insertions(+), 19 deletions(-) diff -r 7e5b3ff06f60 drivers/net/virtio_net.c --- a/drivers/net/virtio_net.c Wed Jan 23 22:53:14

On 02/26/2014 05:23 PM, Michael S. Tsirkin wrote: > On Wed, Feb 26, 2014 at 03:11:21PM +0800, Jason Wang wrote: >> > On 02/26/2014 02:32 PM, Qin Chuanyu wrote: >>> > >On 2014/2/26 13:53, Jason Wang wrote: >>>> > >>On 02/25/2014 09:57 PM, Michael S. Tsirkin wrote: >>>>> > >>>On Tue, Feb 25, 2014 at 02:53:58PM +0800, Jason

On 02/26/2014 05:23 PM, Michael S. Tsirkin wrote: > On Wed, Feb 26, 2014 at 03:11:21PM +0800, Jason Wang wrote: >> > On 02/26/2014 02:32 PM, Qin Chuanyu wrote: >>> > >On 2014/2/26 13:53, Jason Wang wrote: >>>> > >>On 02/25/2014 09:57 PM, Michael S. Tsirkin wrote: >>>>> > >>>On Tue, Feb 25, 2014 at 02:53:58PM +0800, Jason

On 02/26/2014 02:32 PM, Qin Chuanyu wrote: > On 2014/2/26 13:53, Jason Wang wrote: >> On 02/25/2014 09:57 PM, Michael S. Tsirkin wrote: >>> On Tue, Feb 25, 2014 at 02:53:58PM +0800, Jason Wang wrote: >>>> We used to stop the handling of tx when the number of pending DMAs >>>> exceeds VHOST_MAX_PEND. This is used to reduce the memory occupation

On 02/26/2014 02:32 PM, Qin Chuanyu wrote: > On 2014/2/26 13:53, Jason Wang wrote: >> On 02/25/2014 09:57 PM, Michael S. Tsirkin wrote: >>> On Tue, Feb 25, 2014 at 02:53:58PM +0800, Jason Wang wrote: >>>> We used to stop the handling of tx when the number of pending DMAs >>>> exceeds VHOST_MAX_PEND. This is used to reduce the memory occupation

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 |

For small packets data copy was observed to take up about 15% CPU time. Switch to build_skb and avoid the copy when using mergeable rx buffers. As a bonus, medium-size skbs that fit in a page will be completely linear. Of course, we now need to lower the lower bound on packet size, to make sure a sane number of skbs fits in rx socket buffer. By how much? I don't know yet. It might also be

For small packets data copy was observed to take up about 15% CPU time. Switch to build_skb and avoid the copy when using mergeable rx buffers. As a bonus, medium-size skbs that fit in a page will be completely linear. Of course, we now need to lower the lower bound on packet size, to make sure a sane number of skbs fits in rx socket buffer. By how much? I don't know yet. It might also be

On 02/25/2014 09:57 PM, Michael S. Tsirkin wrote: > On Tue, Feb 25, 2014 at 02:53:58PM +0800, Jason Wang wrote: >> We used to stop the handling of tx when the number of pending DMAs >> exceeds VHOST_MAX_PEND. This is used to reduce the memory occupation >> of both host and guest. But it was too aggressive in some cases, since >> any delay or blocking of a single packet