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VMemPool - Virtual Memory Pool Management class

, 8 Aug 2002
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If you deal with same size objects in server coding, VMemPool shows a good way for beginners.
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Introduction

As you know, new/delete operations take a lot of CPU time. If you work with servers, CPU time is important. If additional memory is added to the server, then the servers' available memory size will grow in a linear fashion. However CPU's don't behave the same (dual CPU's doesn't necessarily mean twice the speed of a one CPU situation.)
So common server code has it's own efficient memory management system. VMemPool is the one of them for me.

About The Implementation

CVMemPool is generic (template) class since I assumed the client would want a similar usage as new/delete. So, using CVMemPool, you can code like it's a general pointer.

CObj* p = new CObj;

p->do();

delete p;

CVMemPool has it's own 'allocation table' implemented using a circular queue, so you can check if a pointer in a pool is valid using vmIsBadPtr. You can also check how many objects are allocated in the pool using vmGetPoolInfo.

CVMemPool has two template variable, class objT and DWORD _dwPoolSizeT = 1000. _dwPoolSizeT is the size of the pool. You can reconfigure the pool size with this variable. objT should not be important to you. If objT is absent and you have a different class make the object as below.

// suppose CVMemPool is like below. it's not real code.
template <DWORD _dwPoolSizeT = 1000>
class CVMemPool 
{ 
  ... 
};

class CObj1 : public CVMemPool<>
{
 ...
};

class CObj2 : public CVMemPool<>
{
 ...
};

CObj1 c1;
CObj2 c2; // it will share pool with c1 , it is not good. cos i need objT.

As you know, when a compiler sees the last instancing code, the compiler will think c1 and c2 are the same template class layout and so it make only one virtual pool (because CVMemPool<T,F>::ms_pMemPool is static.)

Usage

//make class in pool.
class CObj : public CVMemPool<CObj>
{
 ...
};

// and you can use it same like general new/delete code.
CObj* p = new CObj; // Pool is created, and allocation in first pool block.
CObj* p2 = new CObj; // second pool block will be used.

delete p; // first block will be freed.
delete p2; // second ,too.

Performance

Test environment

P4 1.6GHz, 256MB ram, Windows 2000 Professional, release executable testing.
Two situations tested:
first, CObj is 1,000 bytes size and loop new and delete 10,000 , 20.000 ....
first, CObj is 10,000 bytes size and loop new and delete 10,000 , 20.000 ....
( n * 1,000 is wrong, n* 10,000 is right, sorry ) The Results are below.

I can't say that these results are exactly right, but I think CVMemPool will be better than the default heap operation (new/delete) on the server side, or on the client side for some CPU's.
In the second situation, I tested 6,000 or over, but I couldn't see the result on the 'Heap' because the program gave a fatal error - insufficient memory - surely, CVMemPool works well and fast. Smile | :)

I hope it help you. Thanks a lot!

Revision History

14 Aug 2002 - Initial revision

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Cho, Kyung-min
Software Developer
Korea (Republic Of) Korea (Republic Of)
No Biography provided

Comments and Discussions

 
Questionhow to alloc object array? Pinmemberapollo.hao10-Nov-11 21:37 
Generalhere is a serious semantic problem about multilayer inheritor [modified] PinmemberHarly8-Nov-10 19:05 
General안녕하세요 이곳에서 같은 나라 분이 짠 코드를 보게되니 재미있네요. PinmemberMatrix is everywhere24-Aug-10 16:15 
GeneralNext small bug found... [modified] Pinmemberlefis27-Sep-08 9:53 
Consider this case:

class CObj: public CVMemPool
{
...
};
 
class CGlobObj
{
CObj * obj;
CGlobObj()
{
obj = new CObj();
}
};
 

/// this will cause surprise around (CSLock) m_csLock inside the CVMemPool class
/// during "new CObj()" call.
CGlobObj bug;
 
int main()
{
...
}

 
When you run your app, initialization begins with 'CGlobObj bug', thus also calling new() on its 'obj' attribute. But call co CSLock() constructor where you are initializing the critical section comes later actually.
So we will probably need to add some static bool to the CVMemPool class, having its default value to false - so it will be initialized before
CGlobObj is initialized. Then, a call to CVMemPool::new() appears; that's the second place for change - you will need to put here a check
if CSLock constructor was called already. If not, assign m_csLock = CSLock(); and set the flag to true. Finally, in the CSLock constructor,
make another check of the flag, not to initialize critical section 2-times.
 
But overall - I am afraid of usage of this CVMemPool with such kind of static objects. With example above, you have to treat with late initialization of CBitSet as well - in the time, when the bits are already allocated, constructor makes "= NULL" -> memory leak.
 
modified on Saturday, September 27, 2008 5:35 PM

Questionmemory problem PinmemberKumara Swamy12-May-07 1:27 
Generalproblem Pinmembercaishaikedou27-Apr-06 17:35 
GeneralAlign with 4 bytes PinmemberAloneInTheCP10-Jan-06 21:13 
AnswerRe: Align with 4 bytes Pinmemberrinzai5-Mar-07 8:34 
GeneralVS.NET 2003 Pinmemberprofix8987-Feb-05 6:17 
GeneralRe: VS.NET 2003 Pinmemberrabidusprocella10-May-05 23:33 
QuestiontimeGetTime? Pinmembermadkoala12-Jan-05 19:31 
AnswerRe: timeGetTime? PinsussAnonymous14-Jan-05 18:47 
GeneralBitset PinmemberRonma27-Dec-04 23:04 
GeneralRe: Bitset PinmemberCho, Kyung-min1-Jan-05 9:09 
GeneralGreat code. Small bug found, and enhancement suggestion. Pinmemberprcarp14-Jan-04 5:48 
GeneralRe: Great code. Small bug found, and enhancement suggestion. PinmemberCho, Kyung-min14-Jan-04 14:27 
GeneralRe: Great code. Small bug found, and enhancement suggestion. Pinmemberrobosport19-Jul-04 16:52 
GeneralRe: Great code. Small bug found, and enhancement suggestion. Pinmemberprcarp20-Jul-04 9:05 
GeneralRe: Great code. Small bug found, and enhancement suggestion. PinmemberHarly8-Nov-10 14:34 
GeneralIssues with the design PinmemberVictor Boctor19-Nov-02 18:02 
GeneralRe: Issues with the design PinmemberTim Smith22-Nov-02 10:15 
GeneralRe: Issues with the design PinmemberCho, Kyung-min16-Dec-02 20:23 
GeneralNo memory is actually allocated PinmemberTim Smith5-Nov-02 9:24 
GeneralLea Allocator PinmemberTim Smith5-Nov-02 9:38 
GeneralRe: No memory is actually allocated PinmemberCho, Kyung-min16-Dec-02 20:15 
GeneralMem allocation Pinmemberbk27-Aug-02 18:26 
GeneralRe: Mem allocation PinmemberCho, Kyung-min29-Aug-02 14:35 
GeneralSmartheap PinmemberSimon Capewell21-Aug-02 2:53 
GeneralRe: Smartheap Pinmemberdrunin5-May-04 6:50 
GeneralRe: Smartheap PinmemberSimon Capewell5-May-04 8:03 
GeneralGreat performance! PinmemberAlbert van Peppen14-Aug-02 5:57 
GeneralRe: Great performance! PinmemberCho, Kyung-min15-Aug-02 15:24 
GeneralImprovment to BitSet.{cpp|h} PinmemberMatthias Mann9-Aug-02 7:45 
GeneralRe: Improvment to BitSet.{cpp|h} PinmemberCho, Kyung-min11-Aug-02 15:45 

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