On Wed, Mar 22, 2017 at 07:50:55AM -0400, Shaohua Li wrote: > On Wed, Mar 22, 2017 at 11:49:00AM +0100, Joerg Roedel wrote: > > Hi Shaohua, > > > > On Tue, Mar 21, 2017 at 11:37:51AM -0700, Shaohua Li wrote: > > > IOMMU harms performance signficantly when we run very fast networking > > > workloads. This is a limitation in hardware based on our observation, so > > > we'd like to disable the IOMMU force on, but we do want to use TBOOT and > > > we can sacrifice the DMA security bought by IOMMU. I must admit I know > > > nothing about TBOOT, but TBOOT guys (cc-ed) think not eabling IOMMU is > > > totally ok. > > > > Can you elaborate a bit more on the setup where the IOMMU still harms > > network performance? With the recent scalability improvements I measured > > only a minimal impact on 10GBit networking. > Hi, > > It's 40GB networking doing XDP test. Software overhead is almost unaware, but > it's the IOTLB miss (based on our analysis) which kills the performance. We > observed the same performance issue even with software passthrough (identity > mapping), only the hardware passthrough survives. The pps with iommu (with > software passthrough) is only about ~30% of that without it.
Hi, Any update on this? Thanks, Shaohua
