Exponential Algorithm In Windows Update Slowing XP Machines

jones_supa writes "An interesting bug regarding update dependency calculation has been found in Windows XP. By design, machines using Windows Update retrieve patch information from Microsoft's update servers (or possibly WSUS in a company setting). That patch information contains information about each patch: what software it applies to and, critically, what historic patch or patches the current patch supersedes. Unfortunately, the Windows Update client components used an algorithm with exponential scaling when processing these lists. Each additional superseded patch would double the time taken to process the list. With the operating system now very old, those lists have grown long, sometimes to 40 or more items. On a new machine, that processing appeared to be almost instantaneous. It is now very slow. After starting the system, svchost.exe is chewing up the entire processor, sometimes for an hour or more at a time. Wait long enough after booting and the machine will eventually return to normalcy. Microsoft thought that it had this problem fixed in November's Patch Tuesday update after it culled the supersedence lists. That update didn't appear to fix the problem. The company thought that its December update would also provide a solution, with even more aggressive culling. That didn't seem to help either. For one reason or another, Microsoft's test scenarios for the patches didn't reflect the experience of real Windows XP machines."

Comments

Re:Remove, replace with apt

[Anonymous Coward]

The dependency system in dpkg has been shown to be powerful enough to express sudoku puzzles which then APT has to solve to resolve conflicts. Technically still potentially exponential with improper use (I trust Microsoft would find some such non-working model reliably).

Re:Ah that explains it

[bmajik]

one thing you can do to fix this is the following

sc config wuauserv type= own

(the space between "type=" and "own" is important)

this tells the service manager to put windows update service (WUAUserv) into its own hosting process, e.g. a new/separate instance of svchost.exe

Another service that can be implicated in updates is the "BITS" service. You can use the same command to isolate it also.

Anytime I see a svchost.exe instance misbehaving I start isolating the services inside it and then seeing which individual service is being problematic.