One of possible problems could be a block size. In this case I am using ZFS with raidZ 4+1 drives. Each drive has 4Kb block. So optimal block size is 16384 bytes. By optimizing block size it possible to improve performance 10 folds but 9p stably provides 10 folds worse performance than native writes.
Some extra tests: --------------------- VM - mapped $ dd if=/dev/zero of=test count=100000 100000+0 records in 100000+0 records out 51200000 bytes (51 MB) copied, 20.7879 s, 2.5 MB/s $ dd if=/dev/zero of=test count=100000 bs=16384 100000+0 records in 100000+0 records out 1638400000 bytes (1.6 GB) copied, 74.4378 s, 22.0 MB/s ------------------------------------------------------------ Host: $ dd if=/dev/zero of=test count=100000 100000+0 records in 100000+0 records out 51200000 bytes (51 MB) copied, 1.60118 s, 32.0 MB/s $ dd if=/dev/zero of=test count=100000 bs=16384 100000+0 records in 100000+0 records out 1638400000 bytes (1.6 GB) copied, 4.89932 s, 334 MB/s Iggy: I has issue with permission in passthrough mode. Can you give an idea how to setup permissions in this mode? -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/965867 Title: 9p virtual file system on qemu slow Status in QEMU: New Status in “qemu-kvm” package in Ubuntu: Confirmed Bug description: Hi, The 9p virtual file system is slow. Several examples below: --------------------------------------------------------- Host for the first time: $ time ls bam.unsorted/ ........................... real 0m0.084s user 0m0.000s sys 0m0.028s -------------------------------------------------- Host second and following: real 0m0.009s user 0m0.000s sys 0m0.008s ------------------------------------------------------ VM for the first time: $ time ls bam.unsorted/ ................................ real 0m23.141s user 0m0.064s sys 0m2.156s ------------------------------------------------------ VM for the second time real 0m3.643s user 0m0.024s sys 0m0.424s ---------------------------------------------------- Copy on host: $ time cp 5173T.root.bak test.tmp real 0m30.346s user 0m0.004s sys 0m5.324s $ ls -lahs test.tmp 2.7G -rw------- 1 oneadmin cloud 2.7G Mar 26 21:47 test.tmp --------------------------------------------------- $ copy on VM for the same file time cp 5173T.root.bak test.tmp real 5m46.978s user 0m0.352s sys 1m38.962s To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/965867/+subscriptions
