RFR(XS) 8059780: SPECjvm2008-MPEG performance regressions on x64 platforms
dean.long at oracle.com
Mon Nov 3 17:40:49 UTC 2014
By the way, do we know why the lcm change caused a regression? Is
reordering the worklist
using pop() a design feature?
On 10/31/2014 5:58 PM, Vladimir Kozlov wrote:
> I forgot to say that lcm.cpp changes were small part of 8052081
> changes. The rest of changes will stay.
> On 10/31/14 5:55 PM, Vladimir Kozlov wrote:
>> We found performance regression (3-5%) on x64 after changes 8052081 
>> were pushed. It is caused by changes in lcm.cpp. Those changes were done
>> because Atom is in-order cpu and some benchmarks on Atom showed benefit
>> from these changes.
>> But Atom is not our core platform and the regression is big.
>> Backout changes made in lcm.cpp in jdk9 and 8u40 (8052081 was backported
>> to 8u40).
>> We have RFEs to improve block's instructions order which may help both
>> Tested with SPECjvm2008-mpegaudio.
>>  https://bugs.openjdk.java.net/browse/JDK-8052081
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