# solved a performance problem in host pattern enumeration **URL:** \ **Category:** Ansible Developer\ **Created:** [October 10, 2013, 1:56pm UTC](https://forum.ansible.com/t/solved-a-performance-problem-in-host-pattern-enumeration/13656 "2013-10-10T13:56:07Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [October 10, 2013, 1:56pm UTC](https://forum.ansible.com/t/solved-a-performance-problem-in-host-pattern-enumeration/13656/1 "2013-10-10T13:56:07Z")
Been running ansible 1.4-devel (a version from september 26, around fd101dd), I yesterday updated to latest (e87be94 22 hours ago 1.3.3 missing from changelog - Michael DeHaan (HEAD, ansible/devel, devel) and noticed a big performance difference. Runnig ansible 20130926: PLAY RECAP \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* Total elapsed time: 0:00:06.829 with ansible 20131010: PLAY RECAP \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* Total elapsed time: 0:00:41.814 (this is from a playbook where tasks are all skipped, so only inventory and local playbook and runner code involved) According to git bisect, this is the patch that introduced the change: 8fc46a3a5a286bee5e429b921ef8af9ea7ecbc31 is the first bad commit commit 8fc46a3a5a286bee5e429b921ef8af9ea7ecbc31 Author: Michael DeHaan \<[michael@ansibleworks.com](mailto:michael@ansibleworks.com)\> Return inventory objects in the order they are presented. Additionally, fix host slicing such that it works on Python terms with zero indexed lists and a non-inclusive final element. I tracked this down to this method, which mentions problem & solution: 250 # TODO: cache this logic so if called a second time the result is not recalculated 251 def \_hosts\_in\_unenumerated\_pattern(self, pattern): Wrote a patch to implement this caching, and things are now even better than before: PLAY RECAP \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\* Total elapsed time: 0:00:03.566 (FYI, my inventory is around 700 hosts in ini files, so these kind of things tend to hit me soon) PR for my patch: [https://github.com/ansible/ansible/pull/4429](https://github.com/ansible/ansible/pull/4429) Serge ---
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [October 10, 2013, 3:07pm UTC](https://forum.ansible.com/t/solved-a-performance-problem-in-host-pattern-enumeration/13656/2 "2013-10-10T15:07:47Z")
I went ahead and merged this, thanks. Thinking we need to make sure this doesn’t confuse usage of the “add\_host” module. I am thinking add\_host usage should maybe invalidate this cache? ---
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [October 11, 2013, 1:59pm UTC](https://forum.ansible.com/t/solved-a-performance-problem-in-host-pattern-enumeration/13656/3 "2013-10-11T13:59:33Z")
​I'll have a look at [https://github.com/ansible/ansible/issues/4442](https://github.com/ansible/ansible/issues/4442) tonight.​ ---
**Author:** ![Michael\_DeHaan2](https://avatars.discourse-cdn.com/v4/letter/m/da6949/32.png) [@Michael\_DeHaan2](https://forum.ansible.com/u/Michael_DeHaan2)\ **Post date:** [October 11, 2013, 2:00pm UTC](https://forum.ansible.com/t/solved-a-performance-problem-in-host-pattern-enumeration/13656/4 "2013-10-11T14:00:23Z")
I’m taking a look at this right now. I’ll let you know if I can’t resolve it.