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

[Vladimir Ivanov]

Derek,

> 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

The former: 8223213 supersedes 8219233 patchset.

The plan is to use 8219233 as an umbrella for tracking the progress of 
relevant fixes and backports.

Best regards,
Vladimir Ivanov

>> -----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) {} }