Bug 598042 - virtio-blk: Avoid zeroing every request structure
virtio-blk: Avoid zeroing every request structure
Status: CLOSED ERRATA
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: kvm (Show other bugs)
5.6
All Linux
high Severity medium
: rc
: ---
Assigned To: Jes Sorensen
Virtualization Bugs
: ZStream
Depends On: 593369
Blocks: Rhel5KvmTier2 604159
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Reported: 2010-05-31 06:05 EDT by Jes Sorensen
Modified: 2013-01-09 17:39 EST (History)
8 users (show)

See Also:
Fixed In Version: kvm-83-183.el5
Doc Type: Bug Fix
Doc Text:
The virtio-blk back end for qemu-kvm performed unnecessary zeroing of memory on every I/O request, which reduced virtual guest performance. With this update, the virtio-blk back end avoids spurious zeroing of request structures on each I/O request, with the result that guest performance is increased.
Story Points: ---
Clone Of: 593369
Environment:
Last Closed: 2011-01-13 18:35:36 EST
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
CRM:
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:


Attachments (Terms of Use)
Avoid zeroing every request structure in virtio-blk (1.55 KB, patch)
2010-06-10 12:47 EDT, Jes Sorensen
no flags Details | Diff

  None (edit)
Comment 1 Jes Sorensen 2010-06-10 12:47:55 EDT
Created attachment 422972 [details]
Avoid zeroing every request structure in virtio-blk

Backport of upstream commit: de6c8042ec55da18702fa51f09072fcaa315edc3

This is a backport of a fix to not zero every request structure, but
only initialize the fields that are read. My testing using IOZone
on a ramdisk device shows a performance boost of 5-7% with this patch
enabled.
Comment 8 Douglas Silas 2010-07-28 11:39:22 EDT
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.

New Contents:
The virtio-blk back end for qemu-kvm performed unnecessary zeroing of memory on every I/O request, which reduced virtual guest performance. With this update, the virtio-blk back end avoids spurious zeroing of request structures on each I/O request, with the result that guest performance is increased.
Comment 13 errata-xmlrpc 2011-01-13 18:35:36 EST
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0028.html

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