Heap Algorithm Update for Atypically Large Heap Requests (815411)

SYMPTOMS

This fix in the Windows XP Service Pack 1 (SP1) and Windows Server 2003 heap algorithm was released to better handle a particular atypical and uncommon sequence of heap requests by a private, internally developed program that is not commercially available. This program allocated and freed large chunks from the heap tens of thousands of times. The original scope and the size of the improvement for the particular program were mistakenly overstated in a prior version of this article based on an internal test application designed to reproduce the symptom, and is not relevant for any known programs or overall system performance. Typical Windows operation and common business, home, gaming and Internet programs will not be affected by this fix. It is not recommended that you use this fix except to address the specific program.

CAUSE

Windows XP SP1 and Windows Server 2003 contain a general purpose, well understood memory / heap algorithm that delivers fast performance for memory requests made from a broad spectrum of Windows programs. The performance of the algorithm in Windows has been evaluated with many industry benchmarks and by careful analysis of typical end-user operations. As with any general purpose algorithm, an atypical sequence of requests can be tailored. In this instance, the algorithm does not perform optimally. However, because such a sequence is not found in typical Windows programs or the system, you do not have to change the heap algorithm. Changing the heap algorithm does not provide for an improvement in system performance for most users and programs.

This hotfix provides a workaround in the heap algorithm to better handle a particular atypical and uncommon sequence of heap requests. The atypical request pattern was found in a custom-built program that does not bear much resemblance to the vast majority of other Windows programs in existence. The scope and the size of this hotfix is narrowly defined for this one particular program and the workaround has no benefit for the majority of programs or overall system performance.

RESOLUTION

Windows XP service pack information

To resolve this problem, obtain the latest service pack for Microsoft Windows XP. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

322389 How to obtain the latest Windows XP service pack

Hotfix information

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows XP or Windows Server 2003 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

Windows XP

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   28-Feb-2003  19:05  5.1.2600.1177     654,336  Ntdll.dll        

Windows XP 64-Bit Edition Version 2002

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   28-Feb-2003  19:05  5.1.2600.1177   1,508,352  Ntdll.dll        IA64
   28-Feb-2003  14:55  5.1.2600.1177     657,408  Wntdll.dll       X86

Windows Server 2003

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   03-Jun-2003  14:30  5.2.3790.49       716,800  Ntdll.dll        

Windows Server 2003 64-Bit Editions and Windows XP 64-Bit Edition Version 2003

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   03-Jun-2003  14:24  5.2.3790.49     1,524,224  Ntdll.dll        IA64
   03-Jun-2003  14:30  5.2.3790.49       711,168  Wntdll.dll       X86

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Microsoft Windows XP Service Pack 2.

Note This article was revised on 4/12/2003 to more accurately reflect the specific purpose and details of the fix. The original title of this article gave the false impression that this was a problem facing many, if not most, Windows XP users who installed SP1. In fact, the problem affects a very small number of customers who are using a privately designed program that exhibits behavior that the hotfix was created to address. (This article was previously published under the title: "Programs Run Slower After You Install Windows XP SP-1". The contents of the hotfix itself have not changed, only the Knowledge Base documentation was revised for improved accuracy and clarity.