On Wed, 17 Jun 2015 18:47:18 +0200 Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > > On 17/06/2015 18:41, Michael S. Tsirkin wrote: > > On Wed, Jun 17, 2015 at 06:38:25PM +0200, Paolo Bonzini wrote: > >> > >> > >> On 17/06/2015 18:34, Michael S. Tsirkin wrote: > >>> On Wed, Jun 17, 2015 at 06:31:32PM +0200, Paolo Bonzini wrote: > >>>> > >>>> > >>>> On 17/06/2015 18:30, Michael S. Tsirkin wrote: > >>>>> Meanwhile old tools are vulnerable to OOM attacks. > >>>> > >>>> For each vhost device there will be likely one tap interface, > >>>> and I suspect that it takes way, way more than 16KB of memory. > >>> > >>> That's not true. We have a vhost device per queue, all queues > >>> are part of a single tap device. > >> > >> s/tap/VCPU/ then. A KVM VCPU also takes more than 16KB of memory. > > > > That's up to you as a kvm maintainer :) > > Not easy, when the CPU alone requires three (albeit non-consecutive) > pages for the VMCS, the APIC access page and the EPT root. > > > People are already concerned about vhost device > > memory usage, I'm not happy to define our user/kernel interface > > in a way that forces even more memory to be used up. > > So, the questions to ask are: > > 1) What is the memory usage like immediately after vhost is brought > up, apart from these 16K? > > 2) Is there anything in vhost that allocates a user-controllable > amount of memory? > > 3) What is the size of the data structures that support one virtqueue > (there are two of them)? Does it depend on the size of the > virtqueues? > > 4) Would it make sense to share memory regions between multiple vhost > devices? Would it be hard to implement? It would also make memory > operations O(1) rather than O(#cpus). > > Paolo in addition to that could vhost share memmap with KVM i.e. use its memslots instead of duplicating it? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
