VIMAGE UDP memory leak fix

[Robert N. M. Watson]

On 21 Nov 2014, at 09:05, Robert N. M. Watson <rwatson at FreeBSD.ORG> wrote:

> To my mind, the only real concern is whether or not you lose access to resource allocation limits that would previously have been present. On the whole, we've tried to centralise resource limitations on kernel memory allocation in UMA, and it would be great if we could find a nice approach to implementing both per-vimage and per-system allocation limits. One thing I'd pondered in the past was whether we could move to a single zone, with its own limits/etc, but also the ability to pass an optional uma_resourcepool_t that allowed additional limits to be imposed based on some other criteria -- e.g., vimage membership. That strikes me as a somewhat complex proposal that would bring new performance/synchronisation concerns, so isn't necessarily something to act on. However, the upshot is that, although I do not oppose combining the zones, we should be aware that we're eliminating a form of resource partitioning between vimages that we may want to find some other solution for (ideally, an elegant one).

And, to respond to your more general comment: I agree that a decision about removing the NOFREE flag should be made independently of choices about devirtualisation. The former probably should be sorted out at this point, as eliminating NOFREE zones has more general benefits to the kernel, but it would be nice not to depend on that to resolve other problems. It could be that a few of us scratching our heads for a few hours each can resolve whether NOFREE can now be safely removed, in which case we should do so (and then allow quite a lot of baking time before it ships in a release).

Robert