Public bug reported: This change provides a mechanism to reduce the number of MMIO doorbell writes for the NVMe driver. When running in a virtualized environment like QEMU, the cost of an MMIO is quite hefy here. The main idea for the patch is provide the device two memory location locations: 1) to store the doorbell values so they can be lookup without the doorbell MMIO write 2) to store an event index. I believe the doorbell value is obvious, the event index not so much. Similar to the virtio specificaiton, the virtual device can tell the driver (guest OS) not to write MMIO unless you are writing past this value. FYI: doorbell values are written by the nvme driver (guest OS) and the event index is written by the virtual device (host OS). The patch implements a new admin command that will communicate where these two memory locations reside. If the command fails, the nvme driver will work as before without any optimizations.
** Affects: linux (Ubuntu) Importance: Undecided Assignee: Tim Gardner (timg-tpi) Status: In Progress ** Affects: linux (Ubuntu Xenial) Importance: Undecided Assignee: Tim Gardner (timg-tpi) Status: In Progress ** Affects: linux (Ubuntu Yakkety) Importance: Undecided Assignee: Tim Gardner (timg-tpi) Status: In Progress ** Affects: linux (Ubuntu Zesty) Importance: Undecided Assignee: Tim Gardner (timg-tpi) Status: In Progress ** Also affects: linux (Ubuntu Zesty) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Yakkety) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Xenial) Importance: Undecided Status: New ** Changed in: linux (Ubuntu Xenial) Status: New => In Progress ** Changed in: linux (Ubuntu Xenial) Assignee: (unassigned) => Tim Gardner (timg-tpi) ** Changed in: linux (Ubuntu Yakkety) Status: New => In Progress ** Changed in: linux (Ubuntu Yakkety) Assignee: (unassigned) => Tim Gardner (timg-tpi) ** Changed in: linux (Ubuntu Zesty) Status: New => In Progress ** Changed in: linux (Ubuntu Zesty) Assignee: (unassigned) => Tim Gardner (timg-tpi) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1637565 Title: nvme: improve performance for virtual Google NVMe devices To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1637565/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs