On Mon, Feb 11, 2019 at 10:19:17AM -0800, Dave Hansen wrote: > On 2/11/19 9:58 AM, Michael S. Tsirkin wrote: > >>> Really it seems we want a virtio ring so we can pass a batch of these. > >>> E.g. 256 entries, 2M each - that's more like it. > >> That only makes sense for a system that's doing high-frequency, > >> discontiguous frees of 2M pages. Right now, a 2M free/realloc cycle > >> (THP or hugetlb) is *not* super-high frequency just because of the > >> latency for zeroing the page. > > Heh but with a ton of free memory, and a thread zeroing some of > > it out in the background, will this still be the case? > > It could be that we'll be able to find clean pages > > at all times. > > In a systems where we have some asynchrounous zeroing of memory where > freed, non-zeroed memory is sequestered out of the allocator, yeah, that > could make sense. > > But, that's not what we have today. Right. I wonder whether it's smart to build this assumption into a host/guest interface though. > >> A virtio ring seems like an overblown solution to a non-existent problem. > > It would be nice to see some traces to help us decide one way or the other. > > Yeah, agreed. Sounds like we need some more testing to see if these > approaches hit bottlenecks anywhere.
