RFR[S]:8241874 [PPC64] Improve performance of Long.reverseBytes() and Integer.reverseBytes() on Power9

[Doerr, Martin]

Hi again,

testing didn’t show any new issues.

Only the copyright years should get updated before pushing.

Is there already a sponsor or do you want me to push it?

Best regards,
Martin


From: Doerr, Martin
Sent: Dienstag, 14. April 2020 15:26
To: Michihiro Horie <HORIE at jp.ibm.com>; cjashfor at linux.ibm.com
Cc: hotspot-compiler-dev at openjdk.java.net; ppc-aix-port-dev at openjdk.java.net
Subject: RE: RFR[S]:8241874 [PPC64] Improve performance of Long.reverseBytes() and Integer.reverseBytes() on Power9

Hi Corey,

thanks for contributing it. Looks good to me. I’ll run it through our testing and let you know about the results.

Best regards,
Martin


From: ppc-aix-port-dev <ppc-aix-port-dev-bounces at openjdk.java.net<mailto:ppc-aix-port-dev-bounces at openjdk.java.net>> On Behalf Of Michihiro Horie
Sent: Freitag, 10. April 2020 10:48
To: cjashfor at linux.ibm.com<mailto:cjashfor at linux.ibm.com>
Cc: hotspot-compiler-dev at openjdk.java.net<mailto:hotspot-compiler-dev at openjdk.java.net>; ppc-aix-port-dev at openjdk.java.net<mailto:ppc-aix-port-dev at openjdk.java.net>
Subject: Re: RFR[S]:8241874 [PPC64] Improve performance of Long.reverseBytes() and Integer.reverseBytes() on Power9


Hi Corey,

Thank you for sharing your benchmarks. I confirmed your change reduced the elapsed time of the benchmarks by more than 30% on my P9 node. Also, I checked JTREG results, which look no problem.

BTW, I cannot find further points of improvement in your change.

Best regards,
Michihiro


----- Original message -----
From: "Corey Ashford" <cjashfor at linux.ibm.com<mailto:cjashfor at linux.ibm.com>>
To: Michihiro Horie/Japan/IBM at IBMJP
Cc: hotspot-compiler-dev at openjdk.java.net<mailto:hotspot-compiler-dev at openjdk.java.net>, ppc-aix-port-dev at openjdk.java.net<mailto:ppc-aix-port-dev at openjdk.java.net>, "Gustavo Romero" <gromero at linux.vnet.ibm.com<mailto:gromero at linux.vnet.ibm.com>>
Subject: Re: RFR[S]:8241874 [PPC64] Improve performance of Long.reverseBytes() and Integer.reverseBytes() on Power9
Date: Fri, Apr 3, 2020 8:07 AM

On 4/2/20 7:27 AM, Michihiro Horie wrote:
> Hi Corey,
>
> I’m not a reviewer, but I can run your benchmark in my local P9 node if
> you share it.
>
> Best regards,
> Michihiro

The tests are somewhat hokey; I added the shifts to keep the compiler
from hoisting the code that it could predetermine the result.

Here's the one for Long.reverseBytes():

import java.lang.*;

class ReverseLong
{
     public static void main(String args[])
     {
         long reversed, re_reversed;
long accum = 0;
long orig = 0x1122334455667788L;
long start = System.currentTimeMillis();
for (int i = 0; i < 1_000_000_000; i++) {
// Try to keep java from figuring out stuff in advance
reversed = Long.reverseBytes(orig);
re_reversed = Long.reverseBytes(reversed);
if (re_reversed != orig) {
         System.out.println("Orig: " + String.format("%16x", orig) +
"  Re-reversed: " + String.format("%16x", re_reversed));
}
accum += orig;
orig = Long.rotateRight(orig, 3);
}
System.out.println("Elapsed time: " +
Long.toString(System.currentTimeMillis() - start));
System.out.println("accum: " + Long.toString(accum));
     }
}


And the one for Integer.reverseBytes():

import java.lang.*;

class ReverseInt
{
     public static void main(String args[])
     {
         int reversed, re_reversed;
int orig = 0x11223344;
int accum = 0;
long start = System.currentTimeMillis();
for (int i = 0; i < 1_000_000_000; i++) {
// Try to keep java from figuring out stuff in advance
reversed = Integer.reverseBytes(orig);
re_reversed = Integer.reverseBytes(reversed);
if (re_reversed != orig) {
         System.out.println("Orig: " + String.format("%08x", orig) +
"  Re-reversed: " + String.format("%08x", re_reversed));
}
accum += orig;
orig = Integer.rotateRight(orig, 3);
}
System.out.println("Elapsed time: " +
Long.toString(System.currentTimeMillis() - start));
System.out.println("accum: " + Integer.toString(accum));
     }
}