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Bug 553719

Summary: Very slow rhel5u3 paravirt guest installations with rhel5u4 z-stream kernel
Product: Red Hat Enterprise Linux 5 Reporter: Gurhan Ozen <gozen>
Component: kernel-xenAssignee: Xen Maintainance List <xen-maint>
Status: CLOSED DUPLICATE QA Contact: Red Hat Kernel QE team <kernel-qe>
Severity: medium Docs Contact:
Priority: medium    
Version: 5.4.zCC: bburns, drjones, emcnabb, jbao, jburke, qcai, rpacheco, xen-maint
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2010-01-12 16:12:35 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Attachments:
Description Flags
/proc/cpuinfo none

Description Gurhan Ozen 2010-01-08 18:31:15 UTC
Description of problem:
This was brought to my attention when the rhts virtualization runs have timed out for the rhel5u3 paravirt guests. It does seem to be on Westmere-EP machines since we haven't yet to see the issue on other machines. 

These are the findings:
   with 2.6.18-164.9.1.el5xen kernel: 
      -fast rhel5u4 pv installs, fast rhel5u hvm install, veryyyy slowwww rhel5u3 pv installs ...
   with 2.6.18-164.el5xen kernel (rhel5u4 release kernel):                        
      - no issues... 
Additionally with 2.6.18-128 kernel: 
      -fast rhel5u3pv kernel 


Version-Release number of selected component (if applicable):
  2.6.18-164.9.1.el5xen

How reproducible:
   Everytime

Steps to Reproduce:
1. Install rhel5u4 on a westmere-EP hardware, install 2.6.18-164.9.1.el5xen kernel and then try to install a rhel5u3 paravirt guest.

Comment 4 Gurhan Ozen 2010-01-08 20:16:50 UTC
Created attachment 382537 [details]
/proc/cpuinfo

Comment 6 Andrew Jones 2010-01-11 07:44:54 UTC
This may be the same issue as in bug 545692. We should try an install using phy (blkback) instead of blktap in the configuration and see if the install is faster. This machine wasn't pingable for me, so I couldn't try it myself right now.

Comment 7 Andrew Jones 2010-01-12 16:12:35 UTC
This is a dup of 545692. I got on the machine and see it has all the same symptoms, including the "blk_tap: invalid kernel buffer -- could not remap it" type logs. I could also install a guest quickly by using a loop device for the backing store, allowing me to use blkback instead of blktap. If I used blktap, it was very, very slow. 

This machine had a 5.3 host, so I installed a 5.3 guest, so it shows that it's not a regression (at least not a recent one). My guess is that this is a bug that is exposed by a particular hardware profile. I'm capturing the profile of this machine to compare against the other machine.

*** This bug has been marked as a duplicate of bug 545692 ***