similar to: network performance degradation in virtio_net in 4.12-rc

On Mon, May 22, 2017 at 10:25:19AM -0400, Mikulas Patocka wrote: > Hi > > I see severe network performance degradation with the kernels 4.12-rc1 and > 4.12-rc2 in the network virtio driver. Download rate drops down to about > 100kB/s. > > I bisected it and it is caused by patch > d85b758f72b05a774045545f24d70980e3e9aac4 ("virtio_net: fix support for > small

commit d85b758f72b0 "virtio_net: fix support for small rings" was supposed to increase the buffer size for small rings but had an unintentional side effect of decreasing it for large rings. This seems to break some setups - it's not yet clear why, but increasing buffer size back to what it was before helps. Fixes: d85b758f72b0 "virtio_net: fix support for small rings"

commit d85b758f72b0 "virtio_net: fix support for small rings" was supposed to increase the buffer size for small rings but had an unintentional side effect of decreasing it for large rings. This seems to break some setups - it's not yet clear why, but increasing buffer size back to what it was before helps. Fixes: d85b758f72b0 "virtio_net: fix support for small rings"

Looks like the culprit is very likely d85b758f72b0 "virtio_net: fix support for small rings". After that patch, my NFS server VM stops responding to packets after a few minutes of testing. Before that patch, my server keeps working. --b.

On Tue, May 30, 2017 at 07:26:37PM +0300, Michael S. Tsirkin wrote: > On Fri, May 26, 2017 at 03:31:33PM -0400, bfields at fieldses.org wrote: > > Looks like the culprit is very likely d85b758f72b0 "virtio_net: fix > > support for small rings". > > > > After that patch, my NFS server VM stops responding to packets after a > > few minutes of testing.

On Tue, May 30, 2017 at 07:26:37PM +0300, Michael S. Tsirkin wrote: > On Fri, May 26, 2017 at 03:31:33PM -0400, bfields at fieldses.org wrote: > > Looks like the culprit is very likely d85b758f72b0 "virtio_net: fix > > support for small rings". > > > > After that patch, my NFS server VM stops responding to packets after a > > few minutes of testing.

On Tue, May 30, 2017 at 07:26:37PM +0300, Michael S. Tsirkin wrote: > On Fri, May 26, 2017 at 03:31:33PM -0400, bfields at fieldses.org wrote: > > Looks like the culprit is very likely d85b758f72b0 "virtio_net: fix > > support for small rings". > > > > After that patch, my NFS server VM stops responding to packets after a > > few minutes of testing.

On Tue, May 30, 2017 at 07:26:37PM +0300, Michael S. Tsirkin wrote: > On Fri, May 26, 2017 at 03:31:33PM -0400, bfields at fieldses.org wrote: > > Looks like the culprit is very likely d85b758f72b0 "virtio_net: fix > > support for small rings". > > > > After that patch, my NFS server VM stops responding to packets after a > > few minutes of testing.

commit d85b758f72b0 ("virtio_net: fix support for small rings") was supposed to increase the buffer size for small rings but had an unintentional side effect of decreasing it for large rings. This seems to break some setups - it's not yet clear why, but increasing buffer size back to what it was before helps. Fixes: d85b758f72b0 ("virtio_net: fix support for small rings")

commit d85b758f72b0 ("virtio_net: fix support for small rings") was supposed to increase the buffer size for small rings but had an unintentional side effect of decreasing it for large rings. This seems to break some setups - it's not yet clear why, but increasing buffer size back to what it was before helps. Fixes: d85b758f72b0 ("virtio_net: fix support for small rings")

When ring size is small (<32 entries) making buffers smaller means a full ring might not be able to hold enough buffers to fit a single large packet. Make sure a ring full of buffers is large enough to allow at least one packet of max size. Fixes: 2613af0ed18a ("virtio_net: migrate mergeable rx buffers to page frag allocators") Signed-off-by: Michael S. Tsirkin <mst at

When ring size is small (<32 entries) making buffers smaller means a full ring might not be able to hold enough buffers to fit a single large packet. Make sure a ring full of buffers is large enough to allow at least one packet of max size. Fixes: 2613af0ed18a ("virtio_net: migrate mergeable rx buffers to page frag allocators") Signed-off-by: Michael S. Tsirkin <mst at

When ring size is small (<32 entries) making buffers smaller means a full ring might not be able to hold enough buffers to fit a single large packet. Make sure a ring full of buffers is large enough to allow at least one packet of max size. Fixes: 2613af0ed18a ("virtio_net: migrate mergeable rx buffers to page frag allocators") Signed-off-by: Michael S. Tsirkin <mst at

When ring size is small (<32 entries) making buffers smaller means a full ring might not be able to hold enough buffers to fit a single large packet. Make sure a ring full of buffers is large enough to allow at least one packet of max size. Fixes: 2613af0ed18a ("virtio_net: migrate mergeable rx buffers to page frag allocators") Signed-off-by: Michael S. Tsirkin <mst at

Probably should have cc'd virtualization at lists.linux-foundation.org too. On Fri, May 26, 2017 at 11:08:39AM -0400, bfields at fieldses.org wrote: > On Tue, May 23, 2017 at 08:23:34AM -0400, bfields at fieldses.org wrote: > > Unfortunately I can't get anything through testing. It's not your > > patches, it's something in -rc1. My server VM stops responding to

Probably should have cc'd virtualization at lists.linux-foundation.org too. On Fri, May 26, 2017 at 11:08:39AM -0400, bfields at fieldses.org wrote: > On Tue, May 23, 2017 at 08:23:34AM -0400, bfields at fieldses.org wrote: > > Unfortunately I can't get anything through testing. It's not your > > patches, it's something in -rc1. My server VM stops responding to

On Wed, 18 Apr 2018, David Miller wrote: > From: Mikulas Patocka <mpatocka at redhat.com> > Date: Wed, 18 Apr 2018 12:44:25 -0400 (EDT) > > > The structure net_device is followed by arbitrary driver-specific data > > (accessible with the function netdev_priv). And for virtio-net, these > > driver-specific data must be in DMA memory. > > And we are saying

On Tue 24-04-18 11:30:40, Mikulas Patocka wrote: > > > On Tue, 24 Apr 2018, Michal Hocko wrote: > > > On Mon 23-04-18 20:25:15, Mikulas Patocka wrote: > > > > > Fixing __vmalloc code > > > is easy and it doesn't require cooperation with maintainers. > > > > But it is a hack against the intention of the scope api. > > It is not!

On Tue 24-04-18 11:30:40, Mikulas Patocka wrote: > > > On Tue, 24 Apr 2018, Michal Hocko wrote: > > > On Mon 23-04-18 20:25:15, Mikulas Patocka wrote: > > > > > Fixing __vmalloc code > > > is easy and it doesn't require cooperation with maintainers. > > > > But it is a hack against the intention of the scope api. > > It is not!

On Wed, 18 Apr 2018, Eric Dumazet wrote: > > > On 04/18/2018 07:34 AM, Mikulas Patocka wrote: > > The patch 74d332c13b21 changes alloc_netdev_mqs to use vzalloc if kzalloc > > fails (later patches change it to kvzalloc). > > > > The problem with this is that if the vzalloc function is actually used, > > virtio_net doesn't work (because it expects