[EXT] Re: [13] RFR (M): 8223213: Implement fast class initialization checks on x86-64

[Derek White]

Hi Vladimir,

I want to be clear on the relationship between bugs and patches:

8223213 and patchset is intended to *replace* 8219233 and it's patchset, or be applied on top of it?
https://bugs.openjdk.java.net/browse/JDK-8223213,
https://bugs.openjdk.java.net/browse/JDK-8219233 

Thanks!
 - Derek

> -----Original Message-----
> From: hotspot-dev <hotspot-dev-bounces at openjdk.java.net> On Behalf Of
> Claes Redestad
> Sent: Thursday, May 02, 2019 7:03 AM
> To: Vladimir Ivanov <vladimir.x.ivanov at oracle.com>; hotspot compiler
> <hotspot-compiler-dev at openjdk.java.net>; hotspot-runtime-dev <hotspot-
> runtime-dev at openjdk.java.net>; hotspot-dev developers <hotspot-
> dev at openjdk.java.net>
> Subject: [EXT] Re: [13] RFR (M): 8223213: Implement fast class initialization
> checks on x86-64
> 
> External Email
> 
> ----------------------------------------------------------------------
> Hi Vladimir,
> 
> On 2019-05-02 01:17, Vladimir Ivanov wrote:
> > Performance experiments with clojure [2] demonstrated that the fix
> > almost completely recuperates the regression:
> >
> >    (1) always reresolve (w/o the fix):    ~12,0s ( 1x)
> >    (2) C1/C2 barriers only:                ~3,8s (~3x)
> >    (3) int/C1/C2 barriers:                 ~3,2s (-20%)
> > --------
> >    (4) barriers disabled for invokestatic  ~3,2s
> 
> good stuff!
> 
> Just to add a few data points I turned some of my earlier experiments to try
> and isolate some of these issues into a little stress test:
> 
> BadStress[1]:
> 11.0.1:                 136ms
> 11.0.2:               13500ms
> jdk/jdk baseline:       126ms
> jdk/jdk patched:        123ms
> 
> GoodStress[2] (baseline):
> 11.0.1:                  56ms
> 11.0.2:                  54ms
> jdk/jdk baseline:        48ms
> jdk/jdk patched:         47ms
> 
> Observations:
> 
>   - On latest jdk/jdk, we've already recuperated most of the cost exposed
>     in these synthetic tests due related fixes (mainly
>     https://bugs.openjdk.java.net/browse/JDK-8188133 and
>     https://bugs.openjdk.java.net/browse/JDK-8219974 ), but the patch
>     helps a bit here too and we're net faster than 11.0.1 (also when
>     taking into account how startup in general has improved since)
> 
>   - The small 1ms startup improvement with the patch on the baseline test
>     is sustained and significant, indicating we have some internal JDK
>     classes exercised during bootstrap which benefit directly from your
>     fixes. I've verified this improvement translates to all our other
>     small-app startup tests.
> 
>   - My tests were too naïve to capture all the overheads seen with clj
> 
>   - Likely still good performance advice to avoid heavy lifting in static
>     initializers.
> 
> All in all I think this is a great improvement and hope the added complexity is
> deemed acceptable.
> 
> Thanks!
> 
> /Claes
> 
> [1]
> public class BadStress {
>    static void foo() {}
>    static void bar() {}
>    public static class Helper {
>      static void foo() { BadStress.foo(); }
>    }
>    static {
>      long start = System.nanoTime();
>      for (int i = 0; i < 10_000_000; i++) {
>        Helper.foo();
>      }
>      for (int i = 0; i < 10_000_000; i++) {
>        bar();
>      }
>      long end = System.nanoTime();
>      System.out.println("Elapsed: " + (end - start) + " ns");
>    }
>    public static void main(String... args) {} }
> 
> [2]
> public class GoodStress {
>    public static class Helper {
>      static void foo() {}
>      static void bar() {}
>    }
>    static {
>      long start = System.nanoTime();
>      for (int i = 0; i < 10_000_000; i++) {
>        Helper.foo();
>      }
>      for (int i = 0; i < 10_000_000; i++) {
>        Helper.bar();
>      }
>      long end = System.nanoTime();
>      System.out.println("Elapsed: " + (end - start) + " ns");
>    }
>    public static void main(String... args) {} }