On Thu, Dec 10, 2020 at 5:11 PM Vivek Goyal <vgo...@redhat.com> wrote:
> Conclusion > ----------- > - virtiofs DAX seems to help a lot in many workloads. > > Note, DAX performance well only if data fits in cache window. My total > data is 16G and cache window size is 16G as well. If data is larger > than DAX cache window, then performance of dax suffers a lot. Overhead > of reclaiming old mapping and setting up a new one is very high. Which begs the question: what is the optimal window size? What is the cost per GB of window to the host and guest? Could we measure at what point does a large window size actually make performance worse? > > NAME WORKLOAD Bandwidth IOPS > 9p-none seqread-psync 98.6mb 24.6k > 9p-mmap seqread-psync 97.5mb 24.3k > 9p-loose seqread-psync 91.6mb 22.9k > vtfs-none seqread-psync 98.4mb 24.6k > vtfs-none-dax seqread-psync 660.3mb 165.0k > vtfs-auto seqread-psync 650.0mb 162.5k > vtfs-auto-dax seqread-psync 703.1mb 175.7k > vtfs-always seqread-psync 671.3mb 167.8k > vtfs-always-dax seqread-psync 687.2mb 171.8k > > 9p-none seqread-psync-multi 397.6mb 99.4k > 9p-mmap seqread-psync-multi 382.7mb 95.6k > 9p-loose seqread-psync-multi 350.5mb 87.6k > vtfs-none seqread-psync-multi 360.0mb 90.0k > vtfs-none-dax seqread-psync-multi 2281.1mb 570.2k > vtfs-auto seqread-psync-multi 2530.7mb 632.6k > vtfs-auto-dax seqread-psync-multi 2423.9mb 605.9k > vtfs-always seqread-psync-multi 2535.7mb 633.9k > vtfs-always-dax seqread-psync-multi 2406.1mb 601.5k Seems like in all the -multi tests 9p-none performs consistently better than vtfs-none. Could that be due to the single queue? Thanks, Miklos
