| Message ID | 1563352162-2756-1-git-send-email-jefflexu@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [blktests] block/024: disable IO requests merging | expand |
diff --git a/tests/block/024 b/tests/block/024 index b40a869..0ffc63f 100755 --- a/tests/block/024 +++ b/tests/block/024 @@ -42,6 +42,9 @@ test() { return 1 fi + # Disable IO request merging + echo 2 > /sys/block/nullb0/queue/nomerges + init_times show_times
block/024 works in a way that, if we submit N bio requests and each bio requests will consume M ns, then the total time consumed should be (N * M) ns. However there may be some merging of write bio requests, and thus the value of the "write ticks" filed of "/sys/block/<dev>/stat" may be less than what we expect. For example, running the following script, ```sh modprobe -r null_blk modprobe null_blk queue_mode=2 irqmode=2 completion_nsec=500000 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 cat /sys/block/nullb0/stat ``` and we get output ``` 1 0 8 0 2626 411 28800 1388 0 943 1444 0 0 0 0 ``` In this case, we submit 3600 (1800 * 2) write bio requests, among which 411 bio requests are merged (2626 + 411 * 2 = 3448). Thus we need to disable the merging of bio requests by ``` ``` Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> --- tests/block/024 | 3 +++ 1 file changed, 3 insertions(+)