RFR (S): 8165501: Serial, Parallel and G1 should track the time since last gc for millis_since_last_gc() with full precision

[Ivan Walulya]

Thanks for the clean up.

Looks good.

//Ivan

> On 25 Jun 2020, at 13:44, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi Ivan,
> 
>  thanks for your review!
> 
> On 25.06.20 11:47, Ivan Walulya wrote:
>> Hi Thomas,
>> A few comments below,
>> src/hotspot/share/gc/parallel/psParallelCompact.cpp
>> -  jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
>> -  jlong ret_val = now - _time_of_last_gc;
>> +  jlong now = os::javaTimeNanos();
>> +  jlong ret_val = (now - _time_of_last_gc_ns) / NANOSECS_PER_MILLISEC;
>> |jlong now|  => |jlong now_ns|  i see you do this for most of the variable names that refer to time in Nanossrc/hotspot/share/gc/g1/g1Policy.hpp
>> +  jlong time_of_last_gc() { return _time_of_last_gc_ns; }
>> same as previous comment, better to maintain the _nssrc/hotspot/share/gc/shared/generation.hpp
>>   // Time (in ms) when we were last collected or now if a collection is
>>   // in progress.
>>   virtual jlong time_of_last_gc(jlong now) {
>>     // Both _time_of_last_gc and now are set using a time source
>>     // that guarantees monotonically non-decreasing values provided
>>     // the underlying platform provides such a source. So we still
>>     // have to guard against non-monotonicity.
>>     NOT_PRODUCT(
>>       if (now < _time_of_last_gc_ns) {
>>         log_warning(gc)("time warp: " JLONG_FORMAT " to " JLONG_FORMAT, _time_of_last_gc_ns, now);
>>       }
>>     )
>>     return _time_of_last_gc_ns;
>>   }   virtual void update_time_of_last_gc(jlong now)  {
>>     _time_of_last_gc_ns = now;
>>   }
>> comments should be edited to reflect the changes, in addition to _ns
> 
> I think I caught them all in
> 
> http://cr.openjdk.java.net/~tschatzl/8165501/webrev.1 <http://cr.openjdk.java.net/~tschatzl/8165501/webrev.1>
> 
> no incremental one since almost everything changed anyway, doing another pass at making the code look similar.
> 
> Retested using the mentioned test.
> 
> Thanks,
>  Thomas