Garbage collection performance degrades as database file size increases

Make sure you do not have `SecCollectionTimeout` configured so the issue can be reproduced quickly. # access_log format LogFormat "%t \" %r\ " %>s %b %{SESSIONID}C Time Taken: %D" combined <IfModule mod_security2.c> SecRuleEngine On SecDebugLog logs/modsec_debug.log SecDebugLogLevel 9 SecCookieFormat 0 SecTmpDir /dev/shm/mod_security/ SecDataDir /dev/shm/mod_security/ SecRule REQUEST_COOKIES:SESSIONID !^$ phase:1,id:118,nolog,pass,setsid:%{REQUEST_COOKIES.SESSIONID} SecAction phase:1,id:119,nolog,pass,setvar:SESSION.my_counter=+1 </IfModule> Here is the "client" script: #!/bin/bash for i in `seq 1 10000`; do curl -b "SESSIONID=test$i" localhost/index.html &>/dev/ null done To reproduce, start httpd with the configuration above, run the client script, and then observe the access_log and mod_security debug logs to see the issue happening. Here is a snippet from access_log showing when the slowness starts to happen: [14/Dec/2016:08:38:03 -0500] "GET /index.html HTTP/1.1" 200 test2736 Time Taken: 1512 [14/Dec/2016:08:38:03 -0500] "GET /index.html HTTP/1.1" 200 test2737 Time Taken: 67055 [14/Dec/2016:08:38:03 -0500] "GET /index.html HTTP/1.1" 200 test2738 Time Taken: 121765 [....] [14/Dec/2016:08:38:53 -0500] "GET /index.html HTTP/1.1" 200 6 test8480 Time Taken: 1789 [14/Dec/2016:08:38:53 -0500] "GET /index.html HTTP/1.1" 200 6 test8481 Time Taken: 213163 [14/Dec/2016:08:38:53 -0500] "GET /index.html HTTP/1.1" 200 6 test8482 Time Taken: 435829 [14/Dec/2016:08:38:53 -0500] "GET /index.html HTTP/1.1" 200 6 test8483 Time Taken: 428476 Finally, here is an example of the mod_security debug logging showing garbage collection duration for a long-running request: [14/Dec/2016:08:38:53 --0500] [localhost/sid#7f0be55d13b0][rid#7f0be569fce0][/index.html][4] Garbage collection took 228151 microseconds.