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From 张洁 <zhang...@opi-corp.com>
Subject Memtable Performance Problem
Date Fri, 11 Dec 2009 03:42:25 GMT
When I was doing to write stress test,I found that the throughput is
not stable,from 200request/s to 12000request/s,in single thread
continue write。
final i found problem is NonBlockHashMap in Memtable ,i use
ConcurrentHashMap instead of NonBlockHashMap,and remove synchronized
block below,the stress test is stable。
  
/resolve function in memtable
 synchronized (keyLocks[Math.abs(key.hashCode() % keyLocks.length)])
        {
            int oldSize = oldCf.size();
            int oldObjectCount = oldCf.getColumnCount();
            oldCf.resolve(columnFamily);
            int newSize = oldCf.size();
            int newObjectCount = oldCf.getColumnCount();
            resolveSize(oldSize, newSize);
            resolveCount(oldObjectCount, newObjectCount);
        }


below is my test code,my test server has 2*4=8CPU and 32G Memory

// Decompiled by Jad v1.5.8e. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.geocities.com/kpdus/jad.html
// Decompiler options: packimports(3) 
// Source File Name:   RowApplyTest.java

import java.io.IOException;
import java.io.PrintStream;
import java.util.concurrent.atomic.AtomicLong;
import org.apache.cassandra.db.*;

public class RowApplyTest
{

    public RowApplyTest()
    {
    }

    public static Column column(String name, String value, long
timestamp)
    {
        return new Column(name.getBytes(), value.getBytes(), timestamp);
    }

    private static void printer()
    {
        Thread t = new Thread(new Runnable() {

            public void run()
            {
                do
                {
                    long current = RowApplyTest._count.get();
                    System.out.println((new StringBuilder("Rate:
")).append(current - _last).append(" req/s").toString());
                    _last = current;
                    try
                    {
                        Thread.sleep(1000L);
                    }
                    catch(InterruptedException e)
                    {
                        e.printStackTrace();
                    }
                } while(true);
            }

            private long _last =0L;
        });
        t.start();
    }

    public static void main(String args[])
        throws IOException
    {
        printer();
        Table table = Table.open("Keyspace1");
        ColumnFamilyStore cfStore =
table.getColumnFamilyStore("Standard1");
        String value = "Agile testing(\u654F\u6377\u6D4B\u8BD5)\u57FA
\u672C\u4E0A\u662F\u4F34\u968F\u7740\u654F\u6377\u5F00\u53D1\u7684\u6982
\u5FF5\u6210\u957F\u8D77\u6765\u7684\uFF0C\u4F46\u5728\u53D7\u5173\u6CE8
\u7A0B\u5EA6\u4E0A\uFF0C\u8FDC\u8FDC\u4E0D\u53CA\u654F\u6377\u5F00\u53D1
\u672C\u8EAB\u3002\u81EA\u7136\uFF0C\u5F00\u53D1\u961F\u4F0D\u4ECE\u6570
\u91CF\u548C\u6D3B\u8DC3\u5EA6\u4E0A\u6765\u8BB2\u5927\u4E8E\u6D4B\u8BD5
\u961F\u4F0D\uFF0C\u662F\u5176\u4E2D\u7684\u4E00\u4E2A\u539F\u56E0\uFF1B
\u9664\u4E86\u8FD9\u4E2A\u539F\u56E0\u4E4B\u5916\uFF0C\u201C\u654F\u6377
\u6D4B\u8BD5\u7A76\u7ADF\u5982\u4F55\u5728\u9879\u76EE\u4E2D\u53D1\u6325
\u4F5C\u7528\u201D\u8FD9\u4E2A\u95EE\u9898\u53EF\u80FD\u4E5F\u662F\u5BFC
\u81F4\u654F\u6377\u6D4B\u8BD5\u6982\u5FF5\u7684\u6D41\u884C\u5EA6\u8FDC
\u8FDC\u4E0D\u5982\u654F\u6377\u5F00\u53D1\u7684\u539F\u56E0\u4E4B\u4E00
\u3002\u5173\u4E8E\u654F\u6377\u6D4B\u8BD5\uFF0C\u6211\u80FD\u627E\u5230
\u7684\u8F83\u65E9\u7684...";
        do
        {
            long i = _count.incrementAndGet();
            String key = (new
StringBuilder("test")).append(i).toString();
            RowMutation rm = new RowMutation("Keyspace1", key);
            ColumnFamily cf = ColumnFamily.create("Keyspace1",
"Standard1");
            cf.addColumn(column("name", value, 1L));
            rm.add(cf);
            rm.apply();
        } while(true);
    }

    private static AtomicLong _count = new AtomicLong(0L);


}

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