Hi Mohan, this parameter provide significant improvement in big file access/write: -------------------------------------------------------------------------------------------- VirtFS on /srv/shared type 9p (rw,trans=virtio,version=9p2000.L,msize=262144)
$ dd if=/dev/zero of=test count=100000 bs=16384 100000+0 records in 100000+0 records out 1638400000 bytes (1.6 GB) copied, 36.3589 s, 45.1 MB/s l$ dd if=/dev/zero of=test count=100000 100000+0 records in 100000+0 records out 51200000 bytes (51 MB) copied, 25.6597 s, 2.0 MB/s $ dd if=/dev/zero of=test count=1024 bs=262144 1024+0 records in 1024+0 records out 268435456 bytes (268 MB) copied, 3.41936 s, 78.5 MB/s Speed of copy for large file ~45MB/s (read and write from the same disk). --------------------------------------------------------------------------------------------- But Host: time ls -lahs bam.unsorted/ many files: real 0m0.053s user 0m0.004s sys 0m0.036s VM: real 0m4.449s user 0m0.012s sys 0m0.136s -------------------------------------------------------- So we have delays on the first file access. Is it possible to resolve this issue? -- 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