APAR status
Closed as program error.
Error description
IHS 2.0.47 "RewriteMap lookups can use High CPU when thousands of strings are passed as keys to the map lookup
Local fix
We will provide an ifix (which for 2.0.47.1 is not be more than a zip file with a README and replacement mod_rewrite.so) that will have a prerequisite of latest 2.0.47.1 maintenance (PK65782).
Problem summary
**************************************************************** * USERS AFFECTED: mod_rewrite configurations which result in * * thousands of strings passed in as keys to the map lookup * **************************************************************** * PROBLEM DESCRIPTION: Performance of an in-memory cache can * * degrade with large numbers of compared strings. * **************************************************************** * RECOMMENDATION: Apply this fix if high CPU is encountered * * when using rewrite maps. * **************************************************************** mod_rewrite maintains an in-memory cache of comparisons against a rewrite map. Due to the data structure used, performance can degrade as the number of entries in the cache increases. High CPU can occur when there are thousands of elements. The number of elements in the cache is generally much larger than the number of entries in the rewrite map, since the set of unique request URLs can result in a large set of comparisons against the map.
Problem conclusion
The data structure used for the in-memory cache was changed to a hash table, greatly reducing the number of required string comparisons, thus resolving the high CPU when the cache contained thousands of entries.
Temporary fix
Comments
APAR Information
APAR number
PK66755
Reported component name
IBM HTTP SERVER
Reported component ID
5724J0801
Reported release
60I
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2008-05-28
Closed date
2008-06-25
Last modified date
2008-06-25
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
IBM HTTP SERVER
Fixed component ID
5724J0801
Applicable component levels
R60A PSN
UP
R60H PSN
UP
R60P PSN
UP
R60I PSN
UP
R60S PSN
UP
R60W PSN
UP
R60Z PSN
UP
R61A PSN
UP
R61H PSN
UP
R61P PSN
UP
R61I PSN
UP
R61S PSN
UP
R61W PSN
UP
R61Z PSN
UP
[{"Line of Business":{"code":"LOB45","label":"Automation"},"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Product":{"code":"SSEQTJ","label":"IBM HTTP Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"6.0"}]
Document Information
Modified date:
07 September 2022