• Maciej S. Szmigiero's avatar
    KVM: selftests: add a memslot-related performance benchmark · cad347fa
    Maciej S. Szmigiero authored
    
    
    This benchmark contains the following tests:
    * Map test, where the host unmaps guest memory while the guest writes to
    it (maps it).
    
    The test is designed in a way to make the unmap operation on the host
    take a negligible amount of time in comparison with the mapping
    operation in the guest.
    
    The test area is actually split in two: the first half is being mapped
    by the guest while the second half in being unmapped by the host.
    Then a guest <-> host sync happens and the areas are reversed.
    
    * Unmap test which is broadly similar to the above map test, but it is
    designed in an opposite way: to make the mapping operation in the guest
    take a negligible amount of time in comparison with the unmap operation
    on the host.
    This test is available in two variants: with per-page unmap operation
    or a chunked one (using 2 MiB chunk size).
    
    * Move active area test which involves moving the last (highest gfn)
    memslot a bit back and forth on the host while the guest is
    concurrently writing around the area being moved (including over the
    moved memslot).
    
    * Move inactive area test which is similar to the previous move active
    area test, but now guest writes all happen outside of the area being
    moved.
    
    * Read / write test in which the guest writes to the beginning of each
    page of the test area while the host writes to the middle of each such
    page.
    Then each side checks the values the other side has written.
    This particular test is not expected to give different results depending
    on particular memslots implementation, it is meant as a rough sanity
    check and to provide insight on the spread of test results expected.
    
    Each test performs its operation in a loop until a test period ends
    (this is 5 seconds by default, but it is configurable).
    Then the total count of loops done is divided by the actual elapsed
    time to give the test result.
    
    The tests have a configurable memslot cap with the "-s" test option, by
    default the system maximum is used.
    Each test is repeated a particular number of times (by default 20
    times), the best result achieved is printed.
    
    The test memory area is divided equally between memslots, the reminder
    is added to the last memslot.
    The test area size does not depend on the number of memslots in use.
    
    The tests also measure the time that it took to add all these memslots.
    The best result from the tests that use the whole test area is printed
    after all the requested tests are done.
    
    In general, these tests are designed to use as much memory as possible
    (within reason) while still doing 100+ loops even on high memslot counts
    with the default test length.
    Increasing the test runtime makes it increasingly more likely that some
    event will happen on the system during the test run, which might lower
    the test result.
    Signed-off-by: default avatarMaciej S. Szmigiero <maciej.szmigiero@oracle.com>
    Reviewed-by: Andrew Jones's avatarAndrew Jones <drjones@redhat.com>
    Message-Id: <8d31bb3d92bc8fa33a9756fa802ee14266ab994e.1618253574.git.maciej.szmigiero@oracle.com>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    cad347fa