2075569 – Allow memory prealloc from multiple threads [rhel-8.6.0.z]

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Bug 2075569 - Allow memory prealloc from multiple threads [rhel-8.6.0.z]

Summary: Allow memory prealloc from multiple threads [rhel-8.6.0.z]

Keywords:
Status:	CLOSED ERRATA
Alias:	None
Product:	Red Hat Enterprise Linux 8
Classification:	Red Hat
Component:	libvirt
Sub Component:
Version:	8.6
Hardware:	Unspecified
OS:	Unspecified
Priority:	medium
Severity:	high
Target Milestone:	rc
Target Release:	---
Assignee:	Michal Privoznik
QA Contact:	liang cong
Docs Contact:	Jiri Herrmann
URL:
Whiteboard:
Depends On:	2067126
Blocks:
TreeView+	depends on / blocked

Reported:	2022-04-14 15:09 UTC by RHEL Program Management Team
Modified:	2022-10-21 15:49 UTC (History)
CC List:	14 users (show)
Fixed In Version:	libvirt-8.0.0-5.1.el8
Doc Type:	Enhancement
Doc Text:	.VM memory preallocation using multiple threads You can now define multiple CPU threads for virtual machine (VM) memory allocation in the domain XML configuration, for example as follows: <memoryBacking> <allocation threads='8'/> </memoryBacking> This ensures that more than one thread is used for loading memory pages when starting a VM. As a consequence, VMs with multiple allocation threads configured start significantly faster, especially if the VMs has large amounts of RAM assigned and backed by hugepages.
Clone Of:	2067126
Environment:
Last Closed:	2022-08-02 10:01:20 UTC
Type:	Feature Request
Target Upstream Version:
Embargoed:
Dependent Products:

Attachments	(Terms of Use)

Links
System	ID	Private	Priority	Status	Summary	Last Updated
Red Hat Issue Tracker	RHELPLAN-119007	0	None	None	None	2022-04-14 15:16:34 UTC
Red Hat Product Errata	RHSA-2022:5821	0	None	None	None	2022-08-02 10:01:49 UTC

Comment 2 liang cong 2022-04-20 07:37:46 UTC

Preverified with scratch build on rhel8.6:
libvirt-8.0.0-6.el8_rc.5b05e15dc0.x86_64
qemu-kvm-6.2.0-11.module+el8.6.0+14707+5aa4b42d.x86_64

Test steps:
1. Setup host hugepages
sysctl vm.nr_hugepages=1024

2. Define domain xml with memorybacking with below:
  <memoryBacking>
    <hugepages>
      <page size='2048' unit='KiB'/>
    </hugepages>
    <allocation threads='8'/>
  </memoryBacking>



3. Start the guest vm

4. Check the guest vm can boot up and works well.

5. Check the qemu cmdline, that multithread pass through libvirt layer to qemu:
-object {"qom-type":"memory-backend-file","id":"pc.ram","mem-path":"/dev/hugepages/libvirt/qemu/2-vm1","x-use-canonical-path-for-ramblock-id":false,"prealloc":true,"prealloc-threads":8,"size":2147483648}

6. Also check the other scenarios, and did not find issue:
6.1 no huge page
6.2 no multi-thread setting
6.3 working with memfd,anonymous,file source
6.4 working with immdiate, ondemand mode
6.5 negative thread setting with minus, zero, not number, too big number
6.6 working with big thread number
6.7 virsh define --validate

Comment 3 liang cong 2022-05-12 06:08:59 UTC

Verified with:
libvirt-8.0.0-5.1.module+el8.6.0+15027+c62943ab.x86_64
qemu-kvm-6.2.0-11.module+el8.6.0+14707+5aa4b42d.x86_64

Test steps:
1. Setup host hugepages
sysctl vm.nr_hugepages=1024

2. Define domain xml with memorybacking with below:
  <memoryBacking>
    <hugepages/>
    <allocation threads='8'/>
  </memoryBacking>



3. Start the guest vm

4. Check the guest vm can boot up and works well.

5. Check the qemu cmdline, that multithread pass through libvirt layer to qemu:
-object {"qom-type":"memory-backend-file","id":"pc.ram","mem-path":"/dev/hugepages/libvirt/qemu/18-vm1","x-use-canonical-path-for-ramblock-id":false,"prealloc":true,"prealloc-threads":8,"size":2147483648}

6. Also check the other scenarios, and did not find issue:
6.1 no huge page
6.2 no multi-thread setting
6.3 working with memfd,anonymous,file source
6.4 working with immdiate, ondemand mode
6.5 negative thread setting with minus, zero, not number, too big number
6.6 working with big thread number
6.7 virsh define --validate
6.8 working with dimm memory devices

Comment 7 liang cong 2022-05-12 08:30:06 UTC

per comment3, mark it verified

Comment 16 errata-xmlrpc 2022-08-02 10:01:20 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: virt:rhel and virt-devel:rhel security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2022:5821

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