[SERVER-16941] Cache can grow indefinitely under WiredTiger Created: 20/Jan/15  Updated: 14/Apr/16  Resolved: 21/Jul/15

Status: Closed
Project: Core Server
Component/s: Storage, WiredTiger
Affects Version/s: 2.8.0-rc5
Fix Version/s: None

Type: Bug Priority: Major - P3
Reporter: Bruce Lucas (Inactive) Assignee: Bruce Lucas (Inactive)
Resolution: Done Votes: 1
Labels: wiredtiger, wttt
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Attachments: PNG File cache-grows-indefinitely.png    
Issue Links:
Related
related to SERVER-16977 Memory increase trend when running ha... Closed
is related to SERVER-16997 wiredtiger's "bytes currently in the ... Closed
Operating System: ALL
Participants:

 Description   

During a 20-minute run with heavy mixed workload the cache was observed to grow on occasion (2 runs out of about 30) to almost 9 GB, compared to a configured value of 5 GB. An assortment of potentially relevant metrics:

  • at point B the checkpoint enters the second phase where "range of ids pinned" grows.
  • at this point bytes in cache starts growing, and continues growing, apparently indefinitely.
  • at C we begin to page performance declines correspondingly.
  • if run continued beyond 20 minutes growth would have likely resulted on being killed by OOM killer.
  • checkpoint is running longer than it did in runs that didn't experience the issue - typically that third checkpoint completed before the end of the run.
  • the spike in reported cached bytes at A, without corresponding increase in VM, is probably the apparent accounting error from SERVER-16881, which is seen to occur frequently in these runs. However the increase starting at B that is the subject of this ticket is accompanied by an increase in VM, so is likely an unrelated issue.


 Comments   
Comment by Daniel Pasette (Inactive) [ 21/Jul/15 ]

This issue has been fixed in subsequent releases.

Comment by Ian Whalen (Inactive) [ 29/Jun/15 ]

bruce.lucas@10gen.com do you believe this has been fixed? If so, do you know of a particular change in MongoDB or WiredTiger that we believe fixed the issue?

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