Posts

• RE: XCP-ng 8.3 with VM crashing

  As I said before, this is looking like a buggy CPU, and you've proved it, given a week with no incident if CPU8 is excluded.

  posted in Hardware

  A

  andyhhp
  
• RE: Xen ERMS Patch - Call for performance testing

  @olivierlambert

  iperf (-P8) for VM to VM on Xeon Gold 6138
  Before: 25-35 Gbps
  After: 25-39 Gbps

  Seems slightly higher at best, but hard to measure a difference as the performance tend to vary a lot between runs.

  posted in Development

  T

  TeddyAstie
  
• RE: Citrix tools after version 9.0 removed quiesced snapshot

  @vkeven
  XCP-ng 8.1 release note says

  VSS and quiesced snapshots support is removed, because it never worked correctly and caused more harm than good. Note that Windows guest tools version 9 (the default for recent versions of Windows if you install Citrix drivers) already removed VSS support, even for older versions of CH / XCP-ng

  I am not sure if this VSS feature is bound to the PV drivers, or if it also needs hypervisor support. Though it is not recommended to stay on a old version of the guest agent.

  posted in XCP-ng

  T

  TeddyAstie
  
• Xen ERMS Patch - Call for performance testing

  Hello !

  I am looking to get some feedback and evaluation on a performance-related patch for Xen (XCP-ng 8.3 only).
  This patch changes the memcpy implementation of Xen to use the "ERMS variant" (aka REP MOVSB) instead of the current REP MOVSQ+B implementation.
  This is expected to perform better on the vast majority of Intel CPUs and modern AMD ones (Zen3+), but may perform worse on some older AMD CPUs.

  This change may impact the performance of PV drivers (especially network).

  You can find more details regarding this proposed change in : https://github.com/xcp-ng-rpms/xen/pull/54
  This change may be reworked in the future to take more in account the specificities of each CPUs (e.g check presence of ERMS flag).

  Keep in mind that this patched version is experimental and not officially supported.

  Installation :

  # Download repo file for XCP-ng 8.3
  wget https://koji.xcp-ng.org/repos/user/8/8.3/xcpng-users.repo -O /etc/yum.repos.d/xcpng-users.repo
  
  # Installing the patched Xen packages (you should see `.erms` packages)
  yum update --enablerepo=xcp-ng-tae1
  

  You can revert the changes by downgrading the Xen package with the ones in the default repos.

  yum downgrade --disablerepo=xcp-ng-tae1 "xen-*"
  

  TSnake41 opened this pull request in xcp-ng-rpms/xen

  draft Use ERMS variant for memcpy #54

  posted in Development

  T

  TeddyAstie