[Bug 1853042] Re: Ubuntu 18.04 - vm disk i/o performance issue when using file system passthrough

[Andrew Cloke]

** Also affects: qemu
   Importance: Undecided
       Status: New

** Also affects: ubuntu-power-systems
   Importance: Undecided
       Status: New

** No longer affects: qemu

** Changed in: ubuntu-power-systems
     Assignee: (unassigned) => Canonical Server Team (canonical-server)

** Changed in: ubuntu-power-systems
   Importance: Undecided => Medium

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https://bugs.launchpad.net/bugs/1853042

Title:
  Ubuntu 18.04 - vm disk i/o performance issue when using file system
  passthrough

Status in The Ubuntu-power-systems project:
  New
Status in qemu package in Ubuntu:
  New

Bug description:
  == Comment: #0 - I-HSIN CHUNG <address@hidden> - 2019-11-15 12:35:05 ==
  ---Problem Description---
  Ubuntu 18.04 - vm disk i/o performance issue when using file system 
passthrough
   
  Contact Information = address@hidden 
   
  ---uname output---
  Linux css-host-22 4.15.0-1039-ibm-gt #41-Ubuntu SMP Wed Oct 2 10:52:25 UTC 
2019 ppc64le ppc64le ppc64le GNU/Linux (host) Linux ubuntu 4.15.0-65-generic 
#74-Ubuntu SMP Tue Sep 17 17:08:54 UTC 2019 ppc64le ppc64le ppc64le GNU/Linux 
(vm)
   
  Machine Type = p9/ac922 
   
  ---Debugger---
  A debugger is not configured
   
  ---Steps to Reproduce---
   1. Env: Ubuntu 18.04.3 LTS?Genesis kernel linux-ibm-gt - 4.15.0-1039.41?qemu 
1:2.11+dfsg-1ubuntu7.18 ibmcloud0.3 or 1:2.11+dfsg-1ubuntu7.19 
ibm-cloud1?fio-3.15-4-g029b

  2. execute run.sh to run fio benchmark:

  2.1) run.sh:
  #!/bin/bash
    
  for bs in  4k 16m
  do

  for rwmixread in 0 25 50 75 100
  do

  for numjobs in 1 4 16 64
  do
  echo ./fio j1.txt --bs=$bs --rwmixread=$rwmixread --numjobs=$numjobs
  ./fio j1.txt --bs=$bs --rwmixread=$rwmixread --numjobs=$numjobs

  done
  done
  done

  2.2) j1.txt:

  [global]
  direct=1
  rw=randrw
  refill_buffers
  norandommap
  randrepeat=0
  ioengine=libaio
  iodepth=64
  runtime=60

  allow_mounted_write=1

  [job2]
  new_group
  filename=/dev/vdb
  filesize=1000g
  cpus_allowed=0-63
  numa_cpu_nodes=0
  numa_mem_policy=bind:0

  3. performance profile:
  device passthrough performance for the nvme: 
  
http://css-host-22.watson.ibm.com/rundir/nvme_vm_perf_vm/20191011-112156/html/#/measurement/vm/ubuntu
 (I/O bandwidth achieved inside VM in GB/s range)

  file system passthrough
  
http://css-host-22.watson.ibm.com/rundir/nvme_vm_perf_vm/20191106-123613/html/#/measurement/vm/ubuntu
 (I/o bandwidth achieved inside the VM is very low)

  desired performance when using file system passthrough should be similar to 
the device passthrough
   
  Userspace tool common name: fio 
   
  The userspace tool has the following bit modes: should be 64 bit 

  Userspace rpm: ?

  Userspace tool obtained from project website:  na 
   
  *Additional Instructions for address@hidden: 
  -Post a private note with access information to the machine that the bug is 
occuring on.
  -Attach ltrace and strace of userspace application.

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