[DOCS-3177] The per-database RW-lock is not yielded when searching an index Created: 15/Apr/14  Updated: 16/Mar/15  Resolved: 26/Jun/14

Status: Closed
Project: Documentation
Component/s: manual
Affects Version/s: None
Fix Version/s: v1.3.7

Type: Improvement Priority: Minor - P4
Reporter: Mark Callaghan Assignee: Sam Kleinman (Inactive)
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:
Days since reply: 9 years, 33 weeks, 6 days ago

 Description   

The docs at http://smalldatum.blogspot.com/2014/04/mongodb-tokumx-and-innodb-for-disk-io_15.html were not clear to me on three issues:
1) the per-db RW-lock is not yielded from page faults while searching an index.
2) this is only done for "predicted page faults", not real page faults. And I am not suggesting that it should be done on real page faults.
3) a pending write lock request prevents new read requests when the per-db RW-lock is currently locked in read-mode. The FAQ states that W has precedence over read but I think that you should also mention this behavior.

See http://smalldatum.blogspot.com/2014/04/mongodb-tokumx-and-innodb-for-disk-io_15.html for performance results and a brief description of the code.



 Comments   
Comment by Githook User [ 26/Jun/14 ]

Author:

{u'username': u'tychoish', u'name': u'Sam Kleinman', u'email': u'samk@10gen.com'}

Message: DOCS-3177 concurency FAQ updates
Branch: master
https://github.com/mongodb/docs/commit/e06b57ff6cca21fda63bd58429e035d3c7b9c065

Comment by Mark Callaghan [ 15/Apr/14 ]

First link should be http://docs.mongodb.org/manual/faq/concurrency/

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