RFR(L): 8074981 (Integer/FP scalar reduction optimization )

[Vitaly Davidovich]

Oh, the motivation is there! :) However, it's not always a quick process
even if everyone's motivated as there may be changes of consequence.  As a
small example, java 8 virtual memory charge is significantly higher than
java 7 due to metaspace vs permgen differences.  In some cases, this now
requires tweaking java 8 settings in order to keep things running
smoothly.  With a big enough codebase, such migrations are never as quick
as one would hope.

At any rate, yes, I meant loop reduction vectorization.  It seems like a
fairly self-contained change which should be relatively painless to
backport, hence my inquiry.

On Tue, Apr 7, 2015 at 3:04 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com>
wrote:

> We want to motivate people to migrate to new releases :)
> If you mean loop reduction vectorization we can consider it after it is
> tested for some time in jdk9.
>
> Vladimir
>
> On 4/7/15 11:55 AM, Vitaly Davidovich wrote:
>
>> Ok, thanks.  That makes sense for avx512 support, but I think having
>> Michael's changes from this thread sooner would be
>> nice as it's quite likely that users are already running java 8 on
>> hardware where this may have benefit.  Java 9 is
>> still ways away, and even when it's released, the migration process is
>> not always quick (depending on the nature of
>> major changes).  But, if backporting it is messy, it's probably not worth
>> it.
>>
>> On Tue, Apr 7, 2015 at 2:38 PM, Vladimir Kozlov <
>> vladimir.kozlov at oracle.com <mailto:vladimir.kozlov at oracle.com>> wrote:
>>
>>     Currently it is only jdk9. There are no plans to backport to 8u.
>>     The thinking is that we will get jdk9 released when this hardware
>> will be widely available.
>>
>>     Regards,
>>     Vladimir
>>
>>     On 4/7/15 11:30 AM, Vitaly Davidovich wrote:
>>
>>         Hi Michael/Vladimir,
>>
>>         Out of curiosity, is this change and the out-for-review avx512
>> one going to be (or planned on being) backported
>>         to java 8?
>>
>>         Thanks
>>
>>         On Tue, Apr 7, 2015 at 2:07 PM, Berg, Michael C <
>> michael.c.berg at intel.com <mailto:michael.c.berg at intel.com>
>>         <mailto:michael.c.berg at intel.__com <mailto:michael.c.berg at intel.
>> com>>> wrote:
>>
>>              Please ignore this one its already checked in…____
>>
>>              __ __
>>
>>              *From:* hotspot-compiler-dev [mailto:hotspot-compiler-dev-_
>> _bounces at openjdk.java.net
>>         <mailto:hotspot-compiler-dev-bounces at openjdk.java.net>
>>              <mailto:hotspot-compiler-dev-__bounces at openjdk.java.net
>>         <mailto:hotspot-compiler-dev-bounces at openjdk.java.net>>] *On
>> Behalf Of *Berg, Michael C
>>              *Sent:* Monday, March 16, 2015 2:18 PM
>>              *To:* hotspot-compiler-dev at openjdk.__java.net <mailto:
>> hotspot-compiler-dev at openjdk.java.net>
>>         <mailto:hotspot-compiler-dev at __openjdk.java.net <mailto:
>> hotspot-compiler-dev at openjdk.java.net>>
>>              *Subject:* RFR(L): 8074981 (Integer/FP scalar reduction
>> optimization )____
>>
>>              __ __
>>
>>              Hi All,____
>>
>>              __ __
>>
>>              We would like to contribute the Integer/FP scalar reduction
>> optimization from Intel.____
>>
>>              The contribution is referenced as Bug ID 8074981 as a
>> performance enhancement. ____
>>
>>              __ __
>>
>>              Please review this patch:____
>>
>>              Bug-id: https://bugs.openjdk.java.net/__browse/JDK-8074981
>>         <https://bugs.openjdk.java.net/browse/JDK-8074981> ____
>>
>>              webrev: https://bugs.openjdk.java.net/
>> __secure/attachment/26101/__webrev.zip
>>         <https://bugs.openjdk.java.net/secure/attachment/26101/webrev.zip>
>> ____
>>
>>              __ __
>>
>>              The optimization achieves as much as 2.3x on integer
>> reductions and supports float and double precision
>>              optimizations____
>>
>>              which also have significant optimization uplift an obey
>> strict fp constraints.____
>>
>>              __ __
>>
>>              Nils Eliasson has offered to sponsor this patch.____
>>
>>              __ __
>>
>>              Thanks,____
>>
>>              __ __
>>
>>              -Michael____
>>
>>              __ __
>>
>>
>>
>>
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