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Why concurrent access to FreezeMap is so slow?

kingbo
kingbo
in Help Center
When I test the concurrent access to FreezeMap,I found it is much slower than single-thread method.My code like following:
ObjectAdapterPtr	g_pAdapter;
vector<string> g_GetNamesFromMap(long beginTime,long endTime)
{
	vector<string> back;
	Freeze::ConnectionPtr pConn = Freeze::createConnection(g_pAdapter->getCommunicator(), "db");
	IHisDataMap hisDataMap(pConn, "map");
	
	IHisDataMap::const_iterator pEnd = hisDataMap.upperBoundForTime(endTime);
	IHisDataMap::const_iterator pos;
	for(pos = hisDataMap.lowerBoundForTime(beginTime);pos!=pEnd;++pos)
	{
		back.push_back(pos->first);
	}
	return back;
}
vector<string> g_SetNamesToMap(string name,long time)
{
	Freeze::ConnectionPtr pConn = Freeze::createConnection(g_pAdapter->getCommunicator(), "db");
	IHisDataMap hisDataMap(pConn, "map");

	IHisDataMap::iterator pos = hisDataMap.find(name);	
	if(pos != hisDataMap.end())
	{
		pos.set(time);
	}else
	{
		hisDataMap.insert(make_pair(name, time));	
	}
	
}


void JobThread::run()
{
	m_bRunning = true;
	IceUtil::Time sleepTime = IceUtil::Time::milliSeconds(1000);
	while(true)
	{
		if(!m_bRunning)
		{
			break;
		}else
		{
			vector<string> names = g_GetNamesFromMap(0,ULONG_MAX);
		}
		ThreadControl::sleep(sleepTime);
	}
}

void main()
{
	//Init communicator and g_pAdapter
	.............................
	
	int iThreadNum = 30;
	for(int i=0;i<iThreadNum;++i)
	{
		JobThread pThread = new JobThread();
		pThread->start();
	}
}
1. When iThreadNum = 1, the g_GetNamesFromMap will use 600ms to finish per time. When iThreadNum = 30, it will takes 33s to finish. Is there anything wrong?
2. When some threads are invoking g_GetNamesFromMap, I will call g_SetNamesToMap to update the map. In this case, do I have to serialize the two function or just call g_SetNamesToMap directly?

Comments

  • bernard
    bernard Jupiter, FL
    kingbo wrote:
    1. When iThreadNum = 1, the g_GetNamesFromMap will use 600ms to finish per time. When iThreadNum = 30, it will takes 33s to finish. Is there anything wrong?

    Your code is not very clear to me: each thread is an infinite loop that gets the names and sleeps for one full second? Which time are you measuring?

    In g_GetNamesFromMap, you can avoid creating transactions by using a const map: 
    const IHisDataMap hisDataMap(pConn, "map");
    This could improve performance a little.

    kingbo wrote:
    2. When some threads are invoking g_GetNamesFromMap, I will call g_SetNamesToMap to update the map. In this case, do I have to serialize the two function or just call g_SetNamesToMap directly?

    You don't need to serialize, since you're using separate connections/maps in each function. However, you need to deal with deadlocks. See the Ice manual for details.

    Cheers,
    Bernard
  • kingbo
    kingbo
    vow! So quick response in weekend. Thank you a lot!
    Your code is not very clear to me: each thread is an infinite loop that gets the names and sleeps for one full second? Which time are you measuring?

    In fact,the code is:
    void JobThread::run()
{
	m_bRunning = true;
	IceUtil::Time sleepTime = IceUtil::Time::milliSeconds(1000);
	while(true)
	{
		if(!m_bRunning)
		{
			break;
		}else
		{
			long beginPos = GetTickCount();
			vector<string> names = g_GetNamesFromMap(0,ULONG_MAX);
			long endPos = GetTickCount();
			printf("g_GetNamesFromMap takes %d\n",endPos-beginPos);
		}
		ThreadControl::sleep(sleepTime);
	}
}

    I just tested your suggestion of "const IHisDataMap hisDataMap(pConn, "map");" and found the performence is improved a little but not satisfied. It still takes 20s to 30s per time.:(
  • bernard
    bernard Jupiter, FL
    Another improvement would be to keep a Map opened in your main thread:
    Freeze::ConnectionPtr pConn = Freeze::createConnection(g_pAdapter->getCommunicator(), "db");
	IHisDataMap hisDataMap(pConn, "map");

    This way, you would avoid opening/closing the map all the time.

    Cheers,
    Bernard
  • kingbo
    kingbo
    There is huge distance between 33s and 600ms. I guess I must miss some important configuration in DB_CONFIG. My DB_CONFIG is:
    set_cachesize 0 1073741824 1
    set_lk_max_lockers 40000
    set_lk_max_locks 40000
    set_lk_max_objects 40000
    set_tx_max 20000
    set_lg_bsize 2097152
    set_lg_max 2097152
    set_flags DB_TXN_NOSYNC
    set_flags DB_TXN_WRITE_NOSYNC

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