[PATCH 0/4] Introduce vfio_dma_mapping_perf_test

[Aaron Lewis <aaronlewis@google.com>]

Add a new VFIO selftest, vfio_dma_mapping_perf_test, to provide a
configurable tool for measuring DMA mapping and unmapping latencies.

This selftest introduces command-line parameters to provide a convenient
way to tune the test for specific situations. For example, it can be used
to observe the lengthy unmap times of the Type 1 IOMMU on large memory
regions, or to compare DMA mapping performance between the Type 1 IOMMU
and IOMMUFD. These scenarios can now be easily configured and run via the
command line.

During development, I abandoned an approach where I initialized memfd
globally in main() for all tests. While that allowed memfd to be
initialized once for all test variants, it proved awkward because a
different memfd would be needed for each supported page size (e.g., 4K,
2M, 1G). Also, If a user is only running a single test variant,
pre-allocating all sizes is unnecessary overhead. Therefore, I dropped
that approach in favor of test-local allocation. However, I'm open to
ideas on a better way to handle this.

Aaron Lewis (4):
  vfio: selftests: Introduce vfio_dma_mapping_perf_test
  vfio: selftests: Add memfd test to vfio_dma_mapping_perf_test
  vfio: selftests: Allow a size for vfio_dma_mapping_perf_test
  vfio: selftests: Allow the flag MAP_POPULATE to be set on the cmdline

 tools/testing/selftests/vfio/Makefile         |   1 +
 .../vfio/lib/include/libvfio/iommu.h          |   7 +
 tools/testing/selftests/vfio/lib/iommu.c      |  24 ++
 .../vfio/vfio_dma_mapping_perf_test.c         | 380 ++++++++++++++++++
 4 files changed, 412 insertions(+)
 create mode 100644 tools/testing/selftests/vfio/vfio_dma_mapping_perf_test.c

-- 
2.55.0.rc0.799.gd6f94ed593-goog