VIRTIO_BLK_F_CONFIG_WCE removed from block devices spec

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    • Type: Bug
    • Resolution: Fixed
    • Priority: Critical
    • virtio 1.0 cs04
    • Affects Version/s: virtio 1.0 cs03
    • Environment:

      Paolo Bonzini <pbonzini@redhat.com>

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      Clarify definition of writeback and writethrough caching, clarify the influence of the
      VIRTIO_BLK_F_FLUSH feature on caching, strengthen the requirement for persisting writes to MUST after a VIRTIO_BLK_T_FLUSH request (and in other cases too involving the new features), introduce VIRTIO_BLK_F_FLUSH and VIRTIO_BLK_F_CONFIG_WCE for non-transitional devices.
      https://lists.oasis-open.org/archives/virtio/201508/msg00024.html

      Show
      Clarify definition of writeback and writethrough caching, clarify the influence of the VIRTIO_BLK_F_FLUSH feature on caching, strengthen the requirement for persisting writes to MUST after a VIRTIO_BLK_T_FLUSH request (and in other cases too involving the new features), introduce VIRTIO_BLK_F_FLUSH and VIRTIO_BLK_F_CONFIG_WCE for non-transitional devices. https://lists.oasis-open.org/archives/virtio/201508/msg00024.html
    • Hide

      Accepted by electronic ballot:
      https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=2864

      Fixed in:

      git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@546 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652

      Show
      Accepted by electronic ballot: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=2864 Fixed in: git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@546 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652

      VIRTIO_BLK_F_CONFIG_WCE is important in order to achieve good performance (up to 2x, though more realistically +30-40%) in latency-bound workloads. However, it was removed by mistake together with VIRTIO_BLK_F_FLUSH.

      The lack of this feature means that virtio 1.0 cs02 does not achieve parity with 0.9.

            Assignee:
            Paolo Bonzini (Inactive)
            Reporter:
            Paolo Bonzini (Inactive)
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              Created:
              Updated:
              Resolved: