Public bug reported: Hello,
An upstream bug has been opened on the matter for quite some time now [0]. I can reproduce easily on our production compute node instance, which are trusty host with xenial hwe kernels (4.15.0-101-generic). However due to heavy backport and such, doing real tracing is a bit hard there. I was able to reproduce the behavior on a hwe-bionic kernel as well. Since most of our critical deployments use bcache, I think this is a kinda nasty bug to have. Reproducing the issue is relatively easy with the script provided in the bug [1]. The script used to capture the stats is this one [2]. [0]: https://bugzilla.kernel.org/show_bug.cgi?id=206767 [1]: https://pastebin.ubuntu.com/p/YnnvvSRhXK/ [2]: https://pastebin.ubuntu.com/p/XfVpzg32sN/ ** Affects: linux (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1900438 Title: Bcache bypasse writeback on caching device with fragmentation Status in linux package in Ubuntu: New Bug description: Hello, An upstream bug has been opened on the matter for quite some time now [0]. I can reproduce easily on our production compute node instance, which are trusty host with xenial hwe kernels (4.15.0-101-generic). However due to heavy backport and such, doing real tracing is a bit hard there. I was able to reproduce the behavior on a hwe-bionic kernel as well. Since most of our critical deployments use bcache, I think this is a kinda nasty bug to have. Reproducing the issue is relatively easy with the script provided in the bug [1]. The script used to capture the stats is this one [2]. [0]: https://bugzilla.kernel.org/show_bug.cgi?id=206767 [1]: https://pastebin.ubuntu.com/p/YnnvvSRhXK/ [2]: https://pastebin.ubuntu.com/p/XfVpzg32sN/ To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1900438/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
