When reading data from an EntryLog file, we create a BufferedReadChannel.
In the size() method of BufferedReadChannel, FileChannelImpl.size() is
called, which is a time-consuming operation.
If the EntryLog file has been archived, it is unnecessary to call
FileChannelImpl.size() every time we read from it. We only need to call it
once, cache the result, and reuse it.
This improvement can benefit two cases.
1. DefaultEntryLogger#scanEntryLog, it can help speed up compaction.
2. BufferedReadChannel#read, It can speed up reading entries from the
EntryLog file.
Performance Test.
The entry log f file holds 1GB data.
-rw-r--r--@ 1 horizon staff 1.0G 7 26 17:47 f.log
1. Test DefaultEntryLogger.scanEntryLog (10x performance improvement)
```
public static void main(String[] args) throws IOException {
ServerConfiguration serverConfiguration = new ServerConfiguration();
serverConfiguration.setLedgerDirNames(new
String[]{"/Users/horizon/Downloads/bk1/bk-data"});
DefaultEntryLogger defaultEntryLogger = new
DefaultEntryLogger(serverConfiguration);
long l = System.currentTimeMillis();
AtomicInteger entryCount = new AtomicInteger();
defaultEntryLogger.scanEntryLog(15, new EntryLogScanner() {
@Override
public boolean accept(long ledgerId) {
return true;
}
@Override
public void process(long ledgerId, long offset, ByteBuf entry)
throws IOException {
entryCount.incrementAndGet();
}
});
long spend = System.currentTimeMillis() - l;
System.out.println("Scan entry end, entry count: " +
entryCount.get());
System.out.println("Spend: " + spend);
}
```
Before:
Scan entry end, entry count: 17886769
Spend: 37273
After:
Scan entry end, entry count: 17886769
Spend: 3363
2. Test DefaultEntryLogger.readFromLogChannel (30x performance improvement)
```
public static void main(String[] args) throws IOException {
ServerConfiguration serverConfiguration = new ServerConfiguration();
serverConfiguration.setLedgerDirNames(new
String[]{"/Users/horizon/Downloads/bk1/bk-data"});
DefaultEntryLogger defaultEntryLogger = new
DefaultEntryLogger(serverConfiguration);
long l = System.currentTimeMillis();
BufferedReadChannel channel =
defaultEntryLogger.getChannelForLogId(15);
int pos = 0;
//Read total 1gb data from the BufferedReadChannel.
long gb = 1024 * 1024 * 1024;
ByteBuf byteBuf = ByteBufAllocator.DEFAULT.heapBuffer(10);
while (pos < gb) {
defaultEntryLogger.readFromLogChannel(15, channel, byteBuf, 0);
pos += byteBuf.readableBytes();
byteBuf.clear();
}
long spend = System.currentTimeMillis() - l;
System.out.println("Spend: " + spend);
}
```
Before:
Spend: 69810
After:
Spend: 2338
