RFR 8166848: Performance bug: SystemDictionary - optimization

[Ioi Lam]

I know many people are not fans of macros or templates, but the 
hashtable iteration code is repeated in many places.

For example, the verification code is the same across these two tables:

  352 void PackageEntryTable::verify() {
  353   int element_count = 0;
  354   int max_bucket_count = 0;
  355   for (int index = 0; index < table_size(); index++) {
  356     int bucket_count = 0;
  357     for (PackageEntry* probe = bucket(index);
  358                               probe != NULL;
  359                               probe = probe->next()) {
  360       probe->verify();
  361       element_count++;
  362       bucket_count++;
  363     }
  364     max_bucket_count = MAX2(max_bucket_count, bucket_count);
  365   }
  366   guarantee(number_of_entries() == element_count,
  367             "Verify of Package Entry Table failed");
  368   DEBUG_ONLY(verify_lookup_length(max_bucket_count, "Package Entry Table"));
  369 }

  509 void ModuleEntryTable::verify() {
  510   int element_count = 0;
  511   int max_bucket_count = 0;
  512   for (int i = 0; i < table_size(); i++) {
  513     int bucket_count = 0;
  514     for (ModuleEntry* probe = bucket(i);
  515                               probe != NULL;
  516                               probe = probe->next()) {
  517       probe->verify();
  518       element_count++;
  519       bucket_count++;
  520     }
  521     max_bucket_count = MAX2(max_bucket_count, bucket_count);
  522   }
  523   guarantee(number_of_entries() == element_count,
  524             "Verify of Module Entry Table failed");
  525   DEBUG_ONLY(verify_lookup_length(max_bucket_count, "Module Entry Table"));
  526 }


and void Dictionary::verify() only has a bit more code inside the inner 
loop. How about using a template here. The following is probably not the 
best way to do it (but it compiles :-)

#include <stdio.h>

class Hashtable {
public:
   template <class Table, class Entry> void do_verify() {
     for (int i=0; i<10; i++) { // pseudo code for the table iteration
       void *probe = NULL;      // pseudo code for getting an entry
       Table::verify_entry((Entry*)probe);
     }
   }
};

class MyHashentry {/*...*/};

class MyHashtable : public Hashtable {
public:
   void verify() {
     do_verify<MyHashtable, MyHashentry>();
   }
   static void verify_entry(MyHashentry *probe) {
     // ...
   }
};


Thanks
- Ioi


On 5/15/17 5:30 AM, coleen.phillimore at oracle.com wrote:
>
>> Summary: Check instead that a bucket isn't 10x the average
>>
>> See bug and linked bugs for more details.
>>
>> Tested with RBT nightly tests (tier2-5).
>>
>> open webrev at http://cr.openjdk.java.net/~coleenp/8166848.01/webrev
>> bug link https://bugs.openjdk.java.net/browse/JDK-8166848
>>
>> Thanks,
>> Coleen
>