RFR(M) 8188165: PPC64: Optimize Unsafe.copyMemory and arraycopy

[Gustavo Romero]

Hi,

>[Ping]
>
>On 9/29/17 4:00 PM, Matthew Brandyberry wrote:
>> This is specific to PPC64LE only.
>>
>> The emphasis in the proposed code is on minimizing branches. Thus, 
>> this code makes no attempt to avoid misaligned accesses and each block 
>> is designed to copy as many elements as possible.
>>
>> As one data point, this yields as much as a 13x improvement in 
>> jbyte_disjoint_arraycopy for certain misaligned scenarios.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8188165
>> Webrev: http://cr.openjdk.java.net/~mbrandy/8188165/jdk10/v1/

For the records, Martin already reviewed that change and pointed out some
aspects that need to be improved / addressed in that change. Mainly:

- Avoid adding another stub
- It should not be just a solution for LE (it must work for both endianness)

Additionally, I tested the change using SPECjbb2015 and found a slight regression.

On a POWER8, SMT=8, score of 10 runs:

            Mean max-jOPS   Mean critical-jOPS   SD max-jOPS   SD critical-jOPS
+--------+---------------+--------------------+-------------+------------------+
w/  opto |       24387.6 |             3905.4 |     972.960 |         323.4238 |
+------------------------------------------------------------------------------+
wo/ opto |       24891.7 |             3933.1 |     227.518 |         293.6455 |
+--------+---------------+--------------------+-------------+------------------+

I'll try to address it before OpenJDK 11 rampdown.

Best regards,
Gustavo


[RUNs]

-- w/ opto --

root at pub:~/SPECjbb2015-1.00# for i in 18-04-10_222315-not-reverted 18-04-11_211557-not-reverted 18-04-11_233332-not-reverted 18-04-12_014507-not-reverted 18-04-14_132617-not-reverted 18-04-14_154517-not-reverted 18-04-14_181417-not-reverted 18-04-14_203008-not-reverted 18-04-14_224917-not-reverted 18-04-15_010546-not-reverted; do fgrep "jOPS =" $i/controller.out;done
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 22693, critical-jOPS = 3386
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26793, max-jOPS = 24907, critical-jOPS = 4070
RUN RESULT: hbIR (max attempted) = 28420, hbIR (settled) = 27532, max-jOPS = 24725, critical-jOPS = 4281
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 22416, critical-jOPS = 4321
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26793, max-jOPS = 24907, critical-jOPS = 3777
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 24907, critical-jOPS = 4117
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26793, max-jOPS = 24907, critical-jOPS = 4124
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 24630, critical-jOPS = 3516
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 24907, critical-jOPS = 3663
RUN RESULT: hbIR (max attempted) = 33169, hbIR (settled) = 27674, max-jOPS = 24877, critical-jOPS = 3799


-- wo/ opto --

root at pub:~/SPECjbb2015-1.00# for i in 18-04-11_004013-reverted 18-04-12_040118-reverted 18-04-12_061741-reverted 18-04-12_083821-reverted 18-04-15_025546-reverted 18-04-15_050857-reverted 18-04-15_072246-reverted 18-04-15_093501-reverted 18-04-15_115234-reverted 18-04-15_141256-reverted; do fgrep "jOPS =" $i/controller.out;done
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 24630, critical-jOPS = 4258
RUN RESULT: hbIR (max attempted) = 29485, hbIR (settled) = 28420, max-jOPS = 25062, critical-jOPS = 3839
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26793, max-jOPS = 24907, critical-jOPS = 4056
RUN RESULT: hbIR (max attempted) = 33169, hbIR (settled) = 27674, max-jOPS = 24877, critical-jOPS = 3985
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26793, max-jOPS = 24907, critical-jOPS = 3897
RUN RESULT: hbIR (max attempted) = 28420, hbIR (settled) = 27532, max-jOPS = 25010, critical-jOPS = 4308
RUN RESULT: hbIR (max attempted) = 29485, hbIR (settled) = 28420, max-jOPS = 25357, critical-jOPS = 4096
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 24907, critical-jOPS = 3798
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 24630, critical-jOPS = 3829
RUN RESULT: hbIR (max attempted) = 27674, hbIR (settled) = 26176, max-jOPS = 24630, critical-jOPS = 3265