Bug 1038563 - Higher host cpu usage on achi driver compared ide driver
Summary: Higher host cpu usage on achi driver compared ide driver
Keywords:
Status: CLOSED WONTFIX
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: qemu-kvm
Version: 7.0
Hardware: x86_64
OS: Linux
medium
medium
Target Milestone: rc
: ---
Assignee: John Snow
QA Contact: Yanhui Ma
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2013-12-05 10:56 UTC by Xiaomei Gao
Modified: 2017-11-16 22:21 UTC (History)
9 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
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Clone Of:
Environment:
Last Closed: 2017-11-16 22:21:44 UTC
Target Upstream Version:


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Comment 3 John Snow 2014-07-17 20:42:19 UTC
Pushing back to 7.2.

AHCI is currently in a tech-preview state and is not feature-complete. As such, it's likely to undergo some major refactoring in the near-future as I try to bring this feature into a stable state. I won't be focusing on optimizations in the immediate time frame, so this is more likely a 7.2 target.

Comment 5 John Snow 2015-06-25 18:33:56 UTC
AHCI support is nearly shored up upstream, but performance enhancements will have to wait until QEMU 2.5 and RHEV 7.3.

Comment 8 John Snow 2017-11-16 22:21:44 UTC
AHCI has never really been prioritized for performance improvements. Our official recommend has been that users seeking performance should use virtio-blk-scsi or virtio-blk-pci; that AHCI is perhaps slower than IDE is not of tremendous concern.

That said, if *severe* performance impediments can be observed, I'd like to fix them -- but I should stop pretending it's a priority for the enterprise product as *ATA devices are generally used only to install the OS, and then most management solutions clone their VMs from there.

ATA interfaces are hardly used for our downstream product, and that's the way it ought to be.

As such, I'm going to close this bug for now as "WONTFIX," but if you find anything obviously abhorrently wrong or prohibitively slow, please reopen and I will investigate it.

Further, if anyone manages to find this bug via google and you have good evidence for exactly _what_ is slow, or have new information to contribute, or would like this fixed upstream, please email me and cc the qemu-block list upstream and we will work on resolving this in the FOSS version of this package.

Thanks,
John


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