[PATCH 0/2] [Trusty] (upstream) SRU: LP1616193 vhost-net:

[Dave Chiluk]

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1616193

The Problem: when a host machines memory becomes fragmented to the point where kmalloc order 4 fails, vhost_net_open fails causing virtual machines to start failing.

The Fix: Adds a fall-back to vmalloc when kmalloc fails.  This is similar to what other subsystems do.  This does not relieve the sorce of the fragmentation which is believed to be dentry cache *(vfs.cache.pressure=600, helps but does not eliminate the issue).  Fix was included in 3.15 so not necessary for our other kernels.

The first patch is required in order to fix the bug.

The second patch was a later clean-up of the first patch, and I think it's responsible for inclusion.  However I'll leave that decision to the Team.  

Dave.