** Description changed: In current Ubuntu kernels, PV blkfront drivers have blk-mq enabled by default and cannot use the old I/O scheduler. [Impact] blk-mq is not as fast as the old request-based scheduler for some workloads on HDD disks. [Fix] Amazon Linux has a commit which reintroduces the request-based mode. It disables blk-mq by default but allows it to be switched back on with a kernel parameter. + For B/C this patchset is bigger as it includes the suspend/resume + patches already in X, and a new fixup. These are desirable as the + request mode patch assumes their presence. + [Regression Potential] - Could potentially break xen based disks on AWS. For B/C, the patches also add some code to the xen core around suspend and resume, this code is much smaller and also mirrors code already in Xenial. + Could potentially break xen based disks on AWS. + + For B/C, the patches also add some code to the xen core around suspend + and resume, this code is much smaller and also mirrors code already in + Xenial. [Tests] Tested by AWS for Xenial, and their kernel engineers vetted the patches. I tested the Bionic and Cosmic patchsets with fio, the system appears stable and the IOPS promised for EBS Provisioned IOPS disks were met in my testing. I did an apt update/upgrade and everything worked (no hash-sum mismatches).
** Description changed: In current Ubuntu kernels, PV blkfront drivers have blk-mq enabled by default and cannot use the old I/O scheduler. [Impact] blk-mq is not as fast as the old request-based scheduler for some workloads on HDD disks. [Fix] Amazon Linux has a commit which reintroduces the request-based mode. It disables blk-mq by default but allows it to be switched back on with a kernel parameter. + For X this needs a small patch from upstream for error handling. + For B/C this patchset is bigger as it includes the suspend/resume patches already in X, and a new fixup. These are desirable as the request mode patch assumes their presence. [Regression Potential] - Could potentially break xen based disks on AWS. + Could potentially break xen based disks on AWS. For B/C, the patches also add some code to the xen core around suspend and resume, this code is much smaller and also mirrors code already in Xenial. [Tests] Tested by AWS for Xenial, and their kernel engineers vetted the patches. I tested the Bionic and Cosmic patchsets with fio, the system appears stable and the IOPS promised for EBS Provisioned IOPS disks were met in my testing. I did an apt update/upgrade and everything worked (no hash-sum mismatches). -- 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/1801305 Title: Restore request-based mode to xen-blkfront for AWS kernels Status in linux package in Ubuntu: Confirmed Bug description: In current Ubuntu kernels, PV blkfront drivers have blk-mq enabled by default and cannot use the old I/O scheduler. [Impact] blk-mq is not as fast as the old request-based scheduler for some workloads on HDD disks. [Fix] Amazon Linux has a commit which reintroduces the request-based mode. It disables blk-mq by default but allows it to be switched back on with a kernel parameter. For X this needs a small patch from upstream for error handling. For B/C this patchset is bigger as it includes the suspend/resume patches already in X, and a new fixup. These are desirable as the request mode patch assumes their presence. [Regression Potential] Could potentially break xen based disks on AWS. For B/C, the patches also add some code to the xen core around suspend and resume, this code is much smaller and also mirrors code already in Xenial. [Tests] Tested by AWS for Xenial, and their kernel engineers vetted the patches. I tested the Bionic and Cosmic patchsets with fio, the system appears stable and the IOPS promised for EBS Provisioned IOPS disks were met in my testing. I did an apt update/upgrade and everything worked (no hash-sum mismatches). To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1801305/+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
