From: Sowmini Varadhan <sowmini.varadhan@xxxxxxxxxx> Date: Thu, 11 Dec 2014 15:21:00 -0500 > All this may be true, but it would also be true for Solaris, which > manages to do line-speed (for the exact same setup), so there must be > some other bottleneck going on? They have DMA mapping interfaces which pre-allocate large batches of mapping at a time. > And fwiw, removing the iommu lock contention out of lockstat > did not make any difference to the throughput, which seems to indicate > that the bottleneck is elsewhere. Like I said, it's in the hypervisor IOMMU interfaces implementing the hardware accesses to flush the hardware and adjust the DMA mappings. The lock just shows because the overhead "bubbles" up to the closest non-hypervisor code. -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
