------- Comment From [email protected] 2017-08-17 08:42 EDT------- Those three patches, at least in the kernel I am running, actually make things worse. The characteristics have changed, in what appears to be a general slow-down of disk I/O (it took over 12 hours to hit the first set of sever stalls), but the delays - when they do occur - or much worse. I saw I/Os getting delayed for over 40 minutes.
I have double-checked that the patches are installed. But in spite of having the patch for the delay length (5be6b75610cefd1e21b98a218211922c2feb6e08) the behavior is back to what I was seeing before that patch alone. I'm attaching the combined diff of the changes I made to the kernel. Note, the only difference between the "worse" run and the previous "better" one was the addition of these two patches: 4d608baac5f4e72b033a122b2d6d9499532c3afc "block: Initialize cfqq->ioprio_class in cfq_get_queue()" 142bbdfccc8b3e9f7342f2ce8422e76a3b45beae "cfq: Disable writeback throttling by default" Which I can't explain, as I don't see how either of those should have made this worse. Maybe I need the actual source for your test kernel so I can add my debug-monitoring code and run. With 40-minute delays the debug- monitoring code is technically not needed, as HTX will complain. But if, as I was seeing on the previous kernel, the delays are below 10 minutes then HTX will never notice and there will be no obvious indication of the more subtle issue. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1709889 Title: Ubuntu 17.04: Bug in cfq scheduler, I/Os do not get submitted to adapter for a very long time. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-power-systems/+bug/1709889/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
