1323294 – AVX-2 migration optimisation

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Bug 1323294 - AVX-2 migration optimisation

Summary: AVX-2 migration optimisation

Keywords:
Status:	CLOSED ERRATA
Alias:	None
Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	qemu-kvm-rhev
Sub Component:
Version:	7.3
Hardware:	Unspecified
OS:	Unspecified
Priority:	unspecified
Severity:	unspecified
Target Milestone:	rc
Target Release:	---
Assignee:	Dr. David Alan Gilbert
QA Contact:	Guo, Zhiyi
Docs Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+	depends on / blocked

Reported:	2016-04-01 18:41 UTC by Dr. David Alan Gilbert
Modified:	2016-11-07 21:03 UTC (History)
CC List:	11 users (show)
Fixed In Version:	qemu-kvm-rhev-2.6.0-8.el7
Doc Type:	Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed:	2016-11-07 21:03:57 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)

Links
System	ID	Private	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHBA-2016:2673	0	normal	SHIPPED_LIVE	qemu-kvm-rhev bug fix and enhancement update	2016-11-08 01:06:13 UTC

Comment 2 Amit Shah 2016-04-05 06:13:38 UTC

AVX2 is already supported in Broadwell and Haswell, we should be able to test it.

Note that avx2 support was added, not avx-512.  So maybe the summary should be updated?

Comment 3 Dr. David Alan Gilbert 2016-04-05 08:46:13 UTC

(In reply to Amit Shah from comment #2)
> AVX2 is already supported in Broadwell and Haswell, we should be able to
> test it.
> 
> Note that avx2 support was added, not avx-512.  So maybe the summary should
> be updated?

Yep, you're right, so we should be able to test it on an AVX2 machine which we'll have somewhere.

Comment 4 Amit Shah 2016-04-05 08:51:10 UTC

(In reply to Dr. David Alan Gilbert from comment #3)
> (In reply to Amit Shah from comment #2)
> > AVX2 is already supported in Broadwell and Haswell, we should be able to
> > test it.
> > 
> > Note that avx2 support was added, not avx-512.  So maybe the summary should
> > be updated?
> 
> Yep, you're right, so we should be able to test it on an AVX2 machine which
> we'll have somewhere.

"grep avx2 /proc/cpuinfo" will confirm if the machine has the extensions which this feature uses.

Comment 6 Dr. David Alan Gilbert 2016-05-31 17:58:03 UTC

OK, it looks like we have two problems:
  a) the configure time test gets optimised out with -O2 and decides it can't do AVX2
  b) There's a compile time test in the code that uses it which checks that it has gcc4.9 or better to work around a header bug, but we've only get 4.8.5 in RHEL.  Paolo says that's due to  https://gcc.gnu.org/ml/gcc-patches/2013-06/txt6Tt74laQsp.txt   which we don't seem to have yet.

Comment 11 Miroslav Rezanina 2016-06-21 07:03:35 UTC

Fix included in qemu-kvm-rhev-2.6.0-8.el7

Comment 15 Guo, Zhiyi 2016-08-23 02:46:24 UTC

Move to verified per comment 13 & 14

Comment 17 errata-xmlrpc 2016-11-07 21:03:57 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, 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://rhn.redhat.com/errata/RHBA-2016-2673.html

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