Nowadays, there are increasing requirements to benchmark the performance of dma_map and dma_unmap particually while the device is attached to an IOMMU.
This patchset provides the benchmark infrastruture for streaming DMA mapping. The architecture of the code is pretty much similar with GUP benchmark: * mm/gup_benchmark.c provides kernel interface; * tools/testing/selftests/vm/gup_benchmark.c provides user program to call the interface provided by mm/gup_benchmark.c.
In our case, kernel/dma/map_benchmark.c is like mm/gup_benchmark.c; tools/testing/selftests/dma/dma_map_benchmark.c is like tools/testing/ selftests/vm/gup_benchmark.c
A major difference with GUP benchmark is DMA_MAP benchmark needs to run on a device. Considering one board with below devices and IOMMUs device A ------- IOMMU 1 device B ------- IOMMU 2 device C ------- non-IOMMU
Different devices might attach to different IOMMU or non-IOMMU. To make benchmark run, we can either * create a virtual device and hack the kernel code to attach the virtual device to IOMMU1, IOMMU2 or non-IOMMU. * use the existing driver_override mechinism, unbind device A,B, or c from their original driver and bind them to "dma_map_benchmark" platform_driver or pci_driver for benchmarking.
In this patchset, I prefer to use the driver_override and avoid the various hack in kernel. We can dynamically switch devices behind different IOMMUs to get the performance of dma map on IOMMU or non-IOMMU.
Barry Song (2): dma-mapping: add benchmark support for streaming DMA APIs selftests/dma: add test application for DMA_MAP_BENCHMARK
MAINTAINERS | 6 + kernel/dma/Kconfig | 8 + kernel/dma/Makefile | 1 + kernel/dma/map_benchmark.c | 202 ++++++++++++++++++ tools/testing/selftests/dma/Makefile | 6 + tools/testing/selftests/dma/config | 1 + .../testing/selftests/dma/dma_map_benchmark.c | 72 +++++++ 7 files changed, 296 insertions(+) create mode 100644 kernel/dma/map_benchmark.c create mode 100644 tools/testing/selftests/dma/Makefile create mode 100644 tools/testing/selftests/dma/config create mode 100644 tools/testing/selftests/dma/dma_map_benchmark.c