block: add a test for iostats time with fast I/Os

This is similar to block/018, but all of the I/Os take less than a
jiffy, which tests b57e99b4b8b0 ("block: use nanosecond resolution for
iostat").

Signed-off-by: Omar Sandoval <osandov@fb.com>

diff --git a/tests/block/024 b/tests/block/024
new file mode 100755 (executable)
index 0000000..4f01b7f
--- /dev/null
+++ b/tests/block/024
@@ -0,0 +1,84 @@
+#!/bin/bash
+#
+# Test the iostats counters for time spent doing I/O where each I/O takes < 1
+# jiffy. Regression test for commit b57e99b4b8b0 ("block: use nanosecond
+# resolution for iostat").
+#
+# Copyright (C) 2018 Omar Sandoval
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. tests/block/rc
+. common/null_blk
+
+DESCRIPTION="do I/O faster than a jiffy and check iostats times"
+QUICK=1
+
+requires() {
+       _have_null_blk
+}
+
+init_times() {
+       init_read_ms="$(awk '{ print $4 }' /sys/block/nullb0/stat)"
+       init_write_ms="$(awk '{ print $8 }' /sys/block/nullb0/stat)"
+}
+
+show_times() {
+       read_ms="$(awk '{ print $4 }' /sys/block/nullb0/stat)"
+       write_ms="$(awk '{ print $8 }' /sys/block/nullb0/stat)"
+
+       # Print rounded to the nearest second
+       printf 'read %d s\n' $(((read_ms - init_read_ms + 500) / 1000))
+       printf 'write %d s\n' $(((write_ms - init_write_ms + 500) / 1000))
+}
+
+test() {
+       echo "Running ${TEST_NAME}"
+
+       for ((queue_mode = 1; queue_mode <= 2; queue_mode++)) do
+               local init_read_ms init_write_ms read_ms write_ms
+
+               echo "queue mode $queue_mode"
+
+               # The maximum value for CONFIG_HZ is 1000. I.e., a tick is one
+               # millisecond. So, make each I/O take half a millisecond.
+               if ! _init_null_blk queue_mode="$queue_mode" irqmode=2 \
+                    completion_nsec=500000; then
+                       continue
+               fi
+
+               init_times
+               show_times
+
+               # 1500 * 0.5 ms is 0.75 seconds, allowing for some overhead so
+               # that it rounds to one second.
+               dd if=/dev/nullb0 of=/dev/null bs=4096 iflag=direct count=1500 status=none
+               show_times
+
+               dd if=/dev/zero of=/dev/nullb0 bs=4096 oflag=direct count=1500 status=none
+               show_times
+
+               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 &
+               wait
+               show_times
+
+               _exit_null_blk
+
+               unset init_read_ms init_write_ms read_ms write_ms
+       done
+
+       echo "Test complete"
+}

diff --git a/tests/block/024.out b/tests/block/024.out
new file mode 100644 (file)
index 0000000..7600389
--- /dev/null
+++ b/tests/block/024.out
@@ -0,0 +1,20 @@
+Running block/024
+queue mode 1
+read 0 s
+write 0 s
+read 1 s
+write 0 s
+read 1 s
+write 1 s
+read 2 s
+write 3 s
+queue mode 2
+read 0 s
+write 0 s
+read 1 s
+write 0 s
+read 1 s
+write 1 s
+read 2 s
+write 3 s
+Test complete