[Qemu-devel] [Bug 965867] Re: 9p virtual file system on qemu slow

[M. Mohan Kumar]

Hi Max,

Could you try passing msize=262144 for 9p mount point and post the
results?

Host:
address@hidden media]# ls -lhas file
1.1G -rw-r--r-- 1 root root 1.0G Apr 26 11:05 file

address@hidden media]# dd if=/dev/zero of=file bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 0.700828 s, 1.5 GB/s

address@hidden media]# time cp file file2

real    0m6.353s
user    0m0.007s
sys     0m1.520s

VM:

address@hidden pass]# time cp file 9p_file

real    0m12.261s
user    0m0.154s
sys     0m2.582s

address@hidden pass]# dd if=/dev/zero of=file.9 bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 2.07335 s, 518 MB/s

address@hidden pass]# mount
[snip]
v_pass on /pass type 9p (rw,trans=virtio,version=9p2000.L,msize=262144)
[/snip]

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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

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