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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Memtable Performance Problem
Date Fri, 11 Dec 2009 03:54:30 GMT
even with CHM, resolve is not threadsafe and needs to be synchronized.
 removing the synchronized could cause data loss.  don't do that. :)

On Thu, Dec 10, 2009 at 9:42 PM, 张洁 <zhangjie@opi-corp.com> wrote:
> 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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