[SERVER-16643] extend existing THP warning to THP defrag setting Created: 23/Dec/14  Updated: 05/Sep/18  Resolved: 15/Jan/15

Status: Closed
Project: Core Server
Component/s: Admin, Performance
Affects Version/s: 2.8.0-rc3
Fix Version/s: 3.0.0-rc6

Type: Improvement Priority: Major - P3
Reporter: Asya Kamsky Assignee: Benety Goh
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
depends on SERVER-13482 mongod could warn user if OS transpar... Closed
Related
related to SERVER-17036 db.runCommand({startupWarnings:1}) in... Closed
related to SERVER-27588 Warning to disable defrag of transpar... Closed
is related to SERVER-16269 WiredTiger blocks queries and updates... Closed
is related to SERVER-17522 THP startup warnings can become stale Closed
Backwards Compatibility: Fully Compatible
Participants:

 Description   

We currently check certain system parameters at start-up including high read-ahead and transparent huge pages.

It turns out even if THP are disabled (enabled set to [never]) if defrag is "always" then it impacts mongod when Linux defrags the pages. We should extend the check and the warning to /sys/kernel/mm/transparent_hugepage/defrag



 Comments   
Comment by Githook User [ 15/Jan/15 ]

Author:

{u'username': u'benety', u'name': u'Benety Goh', u'email': u'benety@mongodb.com'}

Message: SERVER-16643 extend linux transparent huge pages to include 'defrag' parameter.

At startup under Linux, mongod will check the following files:

/sys/kernel/mm/transparent_hugepage/enabled
/sys/kernel/mm/transparent_hugepage/defrag

and produce a warning if either of these parameters are set to [always].

The recommended setting is [never] for both parameters. See:

http://docs.mongodb.org/manual/administration/production-notes/#recommended-configuration
Branch: master
https://github.com/mongodb/mongo/commit/6437d63b9dbd5c80295f54a2b6b8af4638051991

Comment by Daniel Pasette (Inactive) [ 23/Dec/14 ]

It was found that this setting has a large impact on some workloads as seen in SERVER-16269.

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