Heap Algorithm Update for Atypically Large Heap Requests

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.

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.

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:

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

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.

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.