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Bug 1123555

Summary:	virtio-mmio is slooowwwww
Product:	[Fedora] Fedora	Reporter:	Richard W.M. Jones <rjones>
Component:	qemu	Assignee:	Fedora Virtualization Maintainers <virt-maint>
Status:	CLOSED WONTFIX	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	22	CC:	amit.shah, berrange, cfergeau, crobinso, drjones, dwmw2, itamar, pbonzini, rjones, scottt.tw, virt-maint
Target Milestone:	---
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-11-04 23:55:11 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	910269

Description Richard W.M. Jones 2014-07-26 11:55:41 UTC

Description of problem:

On x86-64 (laptop, Core i7):

virtio-serial upload rate:      200553666 bytes/sec (191 Mbytes/sec)
virtio-serial download rate:    818819252 bytes/sec (780 Mbytes/sec)
block device writes:            128171758 bytes/sec (122 Mbytes/sec)
block device reads:             135930402 bytes/sec (129 Mbytes/sec)

[I don't yet have a clear explanation for why guest->host
(download) transfers are so much faster than the other way,
but that's not important for this bug.]

On aarch64:

virtio-serial upload rate:      7273232 bytes/sec (6 Mbytes/sec)
virtio-serial download rate:    16629760 bytes/sec (15 Mbytes/sec)
block device writes:            13466009 bytes/sec (12 Mbytes/sec)
block device reads:             17699635 bytes/sec (16 Mbytes/sec)

Version-Release number of selected component (if applicable):

x86-64 test was using qemu-2.0.0-0.1.rc0.fc21.x86_64
aarch test was with upstream qemu from git

How reproducible:

100%

Steps to Reproduce:
1. I'm using this program:
https://github.com/libguestfs/libguestfs/blob/master/tests/qemu/qemu-speed-test.c

Comment 1 Paolo Bonzini 2014-12-10 11:12:52 UTC

I suspect it's not virtio-mmio, but just KVM on ARM.

Comment 2 Jaroslav Reznik 2015-03-03 16:09:15 UTC

This bug appears to have been reported against 'rawhide' during the Fedora 22 development cycle.
Changing version to '22'.

More information and reason for this action is here:
https://fedoraproject.org/wiki/Fedora_Program_Management/HouseKeeping/Fedora22

Comment 3 Cole Robinson 2015-11-04 23:55:11 UTC

I doubt virtio-mmio is going to get any faster since all future work is looking at virtio-pci. So this bug isn't going to generate anything IMO