This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- zesty' to 'verification-done-zesty'. If the problem still exists, change the tag 'verification-needed-zesty' to 'verification-failed-zesty'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-zesty -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1711251 Title: vhost guest network randomly drops under stress (kvm) Status in The Ubuntu-power-systems project: Fix Committed Status in linux package in Ubuntu: Fix Released Status in linux source package in Zesty: Fix Committed Bug description: == SRU Justification == A vhost performance patch was introduced in the 4.10 kernel upstream, and is currently included in the Zesty 4.10 kernel: commit 809ecb9bca6a9424ccd392d67e368160f8b76c92 Author: Jason Wang <jasow...@redhat.com> Date: Mon Dec 12 14:46:49 2016 +0800 vhost: cache used event for better performance -- However I recently hit a functional issue linked to this patch which would cause random guests to lose their network connection under stress. This is not architecture specific and more likely to be hit with high network stress (i.e. lots of uperf instances). The patch author has now reverted this patch upstream: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/vhost?id=8d65843c44269c21e95c98090d9bb4848d473853 which reads: " Revert "vhost: cache used event for better performance" This reverts commit 809ecb9bca6a9424ccd392d67e368160f8b76c92. Since it was reported to break vhost_net. We want to cache used event and use it to check for notification. The assumption was that guest won't move the event idx back, but this could happen in fact when 16 bit index wraps around after 64K entries. Signed-off-by: Jason Wang <jasow...@redhat.com> Acked-by: Michael S. Tsirkin <m...@redhat.com> Signed-off-by: David S. Miller <da...@davemloft.net> " I am requesting this patch to revert the problematic one be pulled into Ubuntu Zesty (anything 4.10+). ---uname output--- Linux p82qvirt 4.10.0-32-generic #36~16.04.1-Ubuntu SMP Wed Aug 9 09:19:19 UTC 2017 ppc64le ppc64le ppc64le GNU/Linux Machine Type = 8247-22L ---Steps to Reproduce--- I can recreate the scenario with the following setup: - on a 20core host, start 20 1core VMs - I have a single linux bridge assigned to all guests using virtio - start a uperf benchmark between each guest pair (10 total) using a high number of uperf nprocs (32) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-power-systems/+bug/1711251/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
