[SERVER-16737] support eviction_dirty_trigger for WiredTiger Created: 06/Jan/15  Updated: 05/Feb/16  Resolved: 26/Jun/15

Status: Closed
Project: Core Server
Component/s: Storage, WiredTiger
Affects Version/s: None
Fix Version/s: 3.1.5

Type: New Feature Priority: Major - P3
Reporter: Mark Callaghan Assignee: Alexander Gorrod
Resolution: Done Votes: 0
Labels: wiredtiger
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
is depended on by SERVER-16665 WiredTiger b-tree uses too much space... Closed
Backwards Compatibility: Fully Compatible
Participants:

 Description   

Discussion started in SERVER-16665. WT supports eviction_dirty_target, eviction_target and eviction_trigger. I also want a setting for eviction_dirty_trigger. With a 144G RAM server I don't want 140G of dirty pages in the WT cache but I need eviction_dirty_trigger and eviction_dirty_target to enforce that. Otherwise, the percentage of dirty data in the cache will approach 100% and if eviction_dirty_trigger is small then eviction might run for a very long time.



 Comments   
Comment by Githook User [ 10/Jun/15 ]

Author:

{u'username': u'agorrod', u'name': u'Alex Gorrod', u'email': u'alexg@wiredtiger.com'}

Message: Add an eviction_dirty_trigger configuration setting.

Allows applications to maintain a low proportion of dirty pages in
the cache, while allowing clean pages to utilize the cache.

While here, alter the minimum allowed dirty trigger and target to
be set as low as 5 percent. Which may be desired for huge caches.

refs SERVER-16737, WT-1350

e Please enter the commit message for your changes. Lines starting
Branch: develop
https://github.com/wiredtiger/wiredtiger/commit/e075e2c9444549e718a98a345fa967cc92c5da09

Comment by Alexander Gorrod [ 10/Jun/15 ]

This isn't exposed via a documented MongoDB configuration setting, it is available via the general wiredTigerEngineConfigString setting.

Comment by Alexander Gorrod [ 10/Jun/15 ]

Support for eviction_dirty_trigger has been added to WiredTiger in:
https://github.com/wiredtiger/wiredtiger/pull/1999

Support is in the latest MongoDB master branch.

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