FIX: Intermittent query slowdowns and corresponding high CPU utilization (835864)


The information in this article applies to:

  • Microsoft SQL Server 2000 Developer Edition
  • Microsoft SQL Server 2000 Standard Edition
  • Microsoft SQL Server 2000 Enterprise Edition
  • Microsoft SQL Server 2000 Personal Edition
  • Microsoft SQL Server 2000 Enterprise Evaluation Edition
  • Microsoft SQL Server 2000 Workgroup Edition
  • Microsoft SQL Server 2000 Desktop Engine (MSDE)
  • Microsoft SQL Server 2000 Developer Edition 64 bit
  • Microsoft SQL Server 2000 Enterprise Edition 64-bit
Bug #: 470933 (SHILOH_BUGS)
Microsoft SQL Server 2000 fixes are distributed as one downloadable file. Because the fixes are cumulative, each new release contains all the hotfixes and all the security fixes that were included in the previous SQL Server 2000 fix release.

SYMPTOMS

You have a workload that is running on a multiprocessor computer that forces SQL Server to perform many memory allocation operations and memory free operations each second (several hundred small batches that require compilation each second, for example). You may notice that a query that typically runs in a certain time takes longer to complete, although the query processes the same amount of data, uses the same query plan, and performs the same amount of I/O. The only noticeable difference is an increase in the CPU time and the elapsed time that it takes to run the query. In extreme cases, you may find that simple queries (such as SET ROWCOUNT 0) might take several hundred milliseconds to run and several hundred milliseconds of CPU time.

RESOLUTION

Service pack information

To resolve this problem, obtain the latest service pack for Microsoft SQL Server 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

290211 How to obtain the latest SQL Server 2000 service pack

Hotfix information

The English version of this hotfix 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. 
   Date         Time   Version            Size    File name
   --------------------------------------------------------------------
   31-May-2003  18:45  2000.80.818.0      78,400  Console.exe      
   28-Oct-2003  04:21  2000.80.873.0     315,968  Custtask.dll     
   02-Oct-2003  20:59  2000.80.867.0      33,340  Dbmslpcn.dll     
   25-Apr-2003  02:12                    786,432  Distmdl.ldf
   25-Apr-2003  02:12                  2,359,296  Distmdl.mdf
   30-Jan-2003  01:55                        180  Drop_repl_hotfix.sql
   12-Sep-2003  03:26  2000.80.859.0   1,905,216  Dtspkg.dll       
   26-Aug-2003  20:16  2000.80.854.0     528,960  Dtspump.dll      
   23-Jun-2003  22:40  2000.80.837.0   1,557,052  Dtsui.dll        
   23-Jun-2003  22:40  2000.80.837.0     639,552  Dtswiz.dll       
   24-Apr-2003  02:51                    747,927  Instdist.sql
   10-Oct-2003  18:52                    745,961  Instmsdb.sql
   03-May-2003  01:56                      1,581  Inst_repl_hotfix.sql
   08-Feb-2003  06:40  2000.80.765.0      90,692  Msgprox.dll      
   01-Apr-2003  02:07                      1,873  Odsole.sql
   05-Apr-2003  01:46  2000.80.800.0      62,024  Odsole70.dll     
   07-May-2003  20:41  2000.80.819.0      25,144  Opends60.dll     
   02-Apr-2003  21:48  2000.80.796.0      57,904  Osql.exe         
   02-Apr-2003  23:15  2000.80.797.0     279,104  Pfutil80.dll     
   04-Aug-2003  18:17                    550,780  Procsyst.sql
   12-Sep-2003  00:37                     12,305  Qfe469315.sql
   22-May-2003  22:57                     19,195  Qfe469571.sql
   20-Jan-2004  00:45                  1,090,380  Replmerg.sql
   06-Sep-2003  07:18  2000.80.858.0     221,768  Replprov.dll     
   16-Jan-2004  01:24  2000.80.908.0     307,784  Replrec.dll      
   16-Jan-2004  01:13  2000.80.908.0     159,813  Replres.rll
   06-Sep-2003  00:00                  1,087,150  Replsys.sql
   13-Aug-2003  16:28                    986,603  Repltran.sql
   02-Jan-2004  19:42  2000.80.904.0     287,304  Rinitcom.dll     
   22-Oct-2003  00:08  2000.80.871.0      57,916  Semnt.dll        
   29-Jul-2003  20:13  2000.80.819.0     492,096  Semobj.dll       
   31-May-2003  18:27  2000.80.818.0     172,032  Semobj.rll
   02-Jan-2004  19:42  2000.80.904.0      53,832  Snapshot.exe     
   09-Dec-2003  20:07                    117,834  Sp3_serv_uni.sql
   16-Jan-2004  01:23  2000.80.908.0      28,672  Sqlagent.dll     
   16-Jan-2004  01:24  2000.80.908.0     311,872  Sqlagent.exe     
   07-Jan-2004  22:38  2000.80.905.0     126,976  Sqlakw32.dll     
   01-Jun-2003  01:01  2000.80.818.0   4,215,360  Sqldmo.dll       
   07-Apr-2003  17:44                     25,172  Sqldumper.exe    
   19-Mar-2003  18:20  2000.80.789.0      28,672  Sqlevn70.rll
   27-Sep-2003  04:42  2000.80.865.0     180,792  Sqlmap70.dll     
   03-Sep-2003  02:56  2000.80.857.0     188,992  Sqlmmc.dll       
   02-Sep-2003  23:03  2000.80.857.0     479,232  Sqlmmc.rll
   22-Oct-2003  00:08  2000.80.871.0     401,984  Sqlqry.dll       
   08-Feb-2003  06:40  2000.80.765.0      57,920  Sqlrepss.dll     
   24-Jan-2004  01:59  2000.80.910.0   7,610,449  Sqlservr.exe     
   25-Jul-2003  21:44  2000.80.845.0     590,396  Sqlsort.dll      
   08-Feb-2003  06:40  2000.80.765.0      45,644  Sqlvdi.dll       
   24-Jan-2004  01:59  2000.80.910.0     106,588  Sqsrvres.dll     
   02-Oct-2003  20:59  2000.80.867.0      33,340  Ssmslpcn.dll     
   01-Jun-2003  01:01  2000.80.818.0      82,492  Ssnetlib.dll     
   01-Jun-2003  01:01  2000.80.818.0      25,148  Ssnmpn70.dll     
   28-Oct-2003  04:21  2000.80.873.0     123,456  Stardds.dll      
   01-Jun-2003  01:01  2000.80.818.0     158,240  Svrnetcn.dll     
   31-May-2003  18:59  2000.80.818.0      76,416  Svrnetcn.exe     
   30-Apr-2003  23:52  2000.80.816.0      45,132  Ums.dll          
   02-Jul-2003  00:19  2000.80.834.0      98,816  Xpweb70.dll
Note Because of file dependencies, the most recent hotfix or feature that contains these files may also contain additional files.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section of this article.

This problem was first corrected in Microsoft SQL Server 2000 Service Pack 4.

MORE INFORMATION

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the Standard Terminology That Is Used to Describe Microsoft Software Updates


Most memory allocation requests in SQL Server are handled by allocating a page from the buffer pool. SQL Server maintains counters to track how many pages have been stolen from the buffer pool to be use as a generic memory buffer instead of a buffer for a database page. The DBCC MEMORYSTATUS command makes part of this information available and is automatically logged in the error log in certain out-of-memory conditions. These numbers are also used to trigger other events in the server, such as the lazywriter process. For additional information about these counters and stolen memory, click the following article number to view the article in the Microsoft Knowledge Base:

271624 INF: Using DBCC MEMORYSTATUS to monitor SQL Server memory usage



On multiprocessor computers, access to these counter values must be serialized. SQL Server serializes the counter values by using a spinlock. With a spinlock, the thread that wants to acquire the spinlock tries to acquire the lock. If the lock is not available, the thread spins in a loop, periodically rechecking the availability of the resource. If the operation that occurs inside the spinlock protection has a very short duration, such as incrementing or decrementing a counter, using a spinlock can be much faster than using a kernel synchronization object and then switching from user mode to kernel mode and back. However, if the spinlock becomes highly contended, a thread may spend more time spinning and trying to acquire the lock than it does performing useful work. Because of this, spinlocks are not a good choice for protecting a heavily-contended data structure.

This hotfix uses a different synchronization mechanism to maintain these counter values. It requires a substantial amount of contention to cause any noticeable delay or increase in CPU time. Typically, you must have a server with 8 or more processors (so that 8 threads are running at the same time) to be able to process a workload that can generate this much contention. This much contention may be more likely to occur if hyperthreading is enabled because it effectively doubles the number of SQL threads that can be running.
Modification Type:MinorLast Reviewed:10/25/2005
Keywords:kbHotfixServer kbQFE kbQFE kbSQLServ2000preSP4fix kbfix kbbug KB835864 kbAudDeveloper
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