[GitHub] [activemq-artemis] franz1981 commented on issue #2646: ARTEMIS-2317 Reuse file buffer wrapper instances to reduce allocations

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franz1981 commented on issue #2646: ARTEMIS-2317 Reuse file buffer wrapper instances to reduce allocations
URL: https://github.com/apache/activemq-artemis/pull/2646#issuecomment-487007870
 
 
   The speed of `Page::read` has been measured by a handrolled test added on `org.apache.activemq.artemis.tests.unit.core.paging.impl.PageTest`:
   ```java
      @Test
      public void testReadSpeedWithNIO() throws Exception {
         recreateDirectory(getTestDir());
         NIOSequentialFileFactory factory = new NIOSequentialFileFactory(getTestDirfile(), 1);
         SequentialFile file = factory.createSequentialFile("00010.page");
   
         Page impl = new Page(new SimpleString("something"), new NullStorageManager(), factory, file, 10);
   
         Assert.assertEquals(10, impl.getPageId());
   
         impl.open();
   
         Assert.assertEquals(1, factory.listFiles("page").size());
   
         SimpleString simpleDestination = new SimpleString("Test");
   
         final int numberOfElements = 10 * 1024 * 1024 / 100;
   
         addPageElements(simpleDestination, impl, numberOfElements);
   
         final int fileSize = impl.getSize();
   
         System.out.println("fileSize = " + fileSize);
   
         impl.sync();
         impl.close();
   
         file = factory.createSequentialFile("00010.page");
   
         file.open();
   
         impl = new Page(new SimpleString("something"), new NullStorageManager(), factory, file, 10);
   
         final int tests = 10;
         final int times = 100;
         NullStorageManager manager = new NullStorageManager();
   
         for( int t = 0; t<tests;t++) {
   
            long totalTime = 0;
   
            for (int m = 0; m<times;m++) {
               final long start = System.nanoTime();
               List<PagedMessage> msgs = impl.read(manager);
               final long elapsed = System.nanoTime() - start;
               totalTime+=elapsed;
               Assert.assertEquals(numberOfElements, msgs.size());
   
               Assert.assertEquals(numberOfElements, impl.getNumberOfMessages());
   
               for (int i = 0; i < msgs.size(); i++) {
                  Assert.assertEquals(simpleDestination, msgs.get(i).getMessage().getAddressSimpleString());
               }
            }
   
            final long totalBytes = fileSize * times;
            final long megaPerSec = (totalBytes * 1000L)/ totalTime;
            System.out.println(megaPerSec + " MB/sec");
            System.gc();
         }
   
   
         impl.delete(null);
   
         Assert.assertEquals(0, factory.listFiles(".page").size());
      }
   ```
   Although it is a naive one, this test stress the best case scenario of `Page::read` ie when a file page is already into the OS page cache.
   

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