From: Masato Suzuki <[email protected]> The total time spent on write I/Os for the 3 dd executions will be at most 1500 * 3 * 0.5ms = 2250ms, that is, 2.25s. Due to system overhead and timer triggers, a total write I/O time larger than this value is generally reported through I/O stat. However, for a system with very low overhead and/or very precise timers, the reported value can be under 2.5s, leading to a rounded value equal to 2s, and not the 3s expected.
To avoid the test to fail due to this problem, increase the number of write I/Os executed so that the total exact I/O time exceeds 2.5s, leading to a rounded value equal to 3s. The change increases the number of I/Os of the second and third dd calls to 1800, leading to an exact write I/O time of (1500 + 1800 * 2) * 0.5 ms = 2.55s. Signed-off-by: Masato Suzuki <[email protected]> --- tests/block/024 | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/tests/block/024 b/tests/block/024 index cf14707..b40a869 100755 --- a/tests/block/024 +++ b/tests/block/024 @@ -53,9 +53,10 @@ test() { dd if=/dev/zero of=/dev/nullb0 bs=4096 oflag=direct count=1500 status=none show_times + # 1800 * 0.5 ms is 0.9 seconds. dd if=/dev/nullb0 of=/dev/null bs=4096 iflag=direct count=1500 status=none & - dd if=/dev/zero of=/dev/nullb0 bs=4096 oflag=direct count=1500 status=none & - dd if=/dev/zero of=/dev/nullb0 bs=4096 oflag=direct count=1500 status=none & + dd if=/dev/zero of=/dev/nullb0 bs=4096 oflag=direct count=1800 status=none & + dd if=/dev/zero of=/dev/nullb0 bs=4096 oflag=direct count=1800 status=none & wait show_times -- 2.20.1
