On Mon, Oct 16, 2017 at 09:22:02AM +1100, Dave Chinner wrote: > On Sat, Oct 14, 2017 at 10:07:51PM -0700, Shaohua Li wrote: > > From: Shaohua Li <shli@xxxxxx> > > > > Basically this is a copy of commit 001e4a8775f6(ext4: implement cgroup > > writeback support). Tested with a fio test, verified writeback is > > throttled against cgroup io.max write bandwidth, also verified moving > > the fio test to another cgroup and the writeback is throttled against > > new cgroup setting. > > > > I created a test for this as attached, please try! I'll send the test out for > > inclusion later. > > Hmmm. The test you appended just checks that bytes get written. > That's pretty much useless for verification of the features you > describe above (throttling rate it correct, dynamic throttle > application as memcg config changes). > > You explicitly state this is a memcg IO QoS feature and that you > have a set of fio tests that verify that it works as expected. We > need those "works as expected" fio tests formalised into automated > fstests. Both upstream fs developers and downstream distro QE > departments need to be able to verify that the bandwidth control and > throttling works as advertised - it's essential that we have > regression tests for this.... Right, this test only verifies the writeback is correctly charged to a cgroup, it doesn't verify the writeback is running in correct bandwidth. I did try to create such automatic test, but my attempt failed. To measure speed, we need measure the time for a test. But writeback is async, the file write finishes before the data is written to disk. We can't call a fsync, because fsync write is different than writeback write, which is charged to correct cgroup even without cgroup writeback support. For my test, I run iostat and check the disk speed is correct, so I don't have idea to create an automatic test. Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
