Re: [PATCH V2] vhost: introduce O(1) vq metadata cache

[Jason Wang]

On 2017å02æ28æ 02:35, Michael S. Tsirkin wrote:
> On Wed, Feb 15, 2017 at 01:37:17PM +0800, Jason Wang wrote:
> > On 2016å12æ14æ 17:53, Jason Wang wrote:
> > > When device IOTLB is enabled, all address translations were stored in
> > > interval tree. O(lgN) searching time could be slow for virtqueue
> > > metadata (avail, used and descriptors) since they were accessed much
> > > often than other addresses. So this patch introduces an O(1) array
> > > which points to the interval tree nodes that store the translations of
> > > vq metadata. Those array were update during vq IOTLB prefetching and
> > > were reset during each invalidation and tlb update. Each time we want
> > > to access vq metadata, this small array were queried before interval
> > > tree. This would be sufficient for static mappings but not dynamic
> > > mappings, we could do optimizations on top.
> > >
> > > Test were done with l2fwd in guest (2M hugepage):
> > >
> > >      noiommu  | before        | after
> > > tx 1.32Mpps | 1.06Mpps(82%) | 1.30Mpps(98%)
> > > rx 2.33Mpps | 1.46Mpps(63%) | 2.29Mpps(98%)
> > >
> > > We can almost reach the same performance as noiommu mode.
> > >
> > > Signed-off-by: Jason Wang<jasowang@xxxxxxxxxx>
> > > ---
> > > Changes from V1:
> > > - silent 32bit build warning
> > ping
> Could you rebase pls?
> I pushed my tree into linux next.

Ok, will do.

Thanks