For the matching kernel patch, see: https://lkml.org/lkml/2018/2/6/866
This series enables ioeventfd support and makes use of a proposed vfio kernel ioeventfd interface for accelerating high frequency writes through to the device. In the specific case addressed, the writes are to a range of MMIO space virtualized in QEMU for NVIDIA GeForce support, but which also hosts a register which is used to allow the MSI interrupt for the device to re-trigger. Applications which generate a very high interrupt rate on the GPU can see noticeable overhead as a result of this trap through QEMU. We added an option for users to disable these quirks entirely for non-Geforce cards[1] for optimal performance, but for GeForce users and users that can't tweak their VM config, this gets us to within 95% of that performance for an interrupt intensive micro-benchmark (from 83%). I'd be interested in more typical benchmark results to understand if there's an improvement there as well. Thanks, Alex [1] https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg06878.html --- Alex Williamson (5): vfio/quirks: Add common quirk alloc helper vfio/quirks: Add generic support for ioveventfds vfio/quirks: Automatic ioeventfd enabling for NVIDIA BAR0 quirks vfio: Update linux header vfio/quirks: Enable ioeventfd quirks to be handled by vfio directly hw/vfio/pci-quirks.c | 184 +++++++++++++++++++++++++++++++++++++------- hw/vfio/pci.h | 13 +++ linux-headers/linux/vfio.h | 24 ++++++ 3 files changed, 192 insertions(+), 29 deletions(-)
