[SERVER-24207] Substantial excess allocated memory and stall in YCSB insert workload associated with very large page Created: 19/May/16  Updated: 15/Jul/16  Resolved: 15/Jul/16

Status: Closed
Project: Core Server
Component/s: WiredTiger
Affects Version/s: 3.3.5, 3.3.6
Fix Version/s: None

Type: Bug Priority: Major - P3
Reporter: Bruce Lucas (Inactive) Assignee: Sulabh Mahajan
Resolution: Done Votes: 0
Labels: RF, WTmem
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Attachments: HTML File timeseries_op_after_fix.html     PNG File ycsb-insert-stall-excess-memory.png    
Issue Links:
Related
is related to SERVER-24076 Excess memory use on PPC64 Closed
Backwards Compatibility: Fully Compatible
Operating System: ALL
Participants:

 Description   
  • 64 GB memory, 24 cpus (12 cores)
  • mongod 3.3.5, standalone, 45 GB cache
  • YCSB workload as follows (in file repro.ycsb):

    fieldcount=3
    recordcount=800000000
    operationcount=400000000
    workload=com.yahoo.ycsb.workloads.CoreWorkload
     
    readallfields=true
     
    readproportion=0.5
    updateproportion=0.5
    scanproportion=0
    insertproportion=0
     
    requestdistribution=zipfian
    

    run as follows:

    ycsb load mongodb -s -P repro.ycsb -threads 30 -p batchsize=1000
    

Some key metrics from a run:

  • stall from A-B immediately followed by
    • large jump in pages held in cache
    • very large maximum page size at eviction (about 10 GB)
    • immediate large jump in excess allocated memory of about the same size (11 GB)
    • excess immediately begins to decline
  • other stalls, e.g. C-D, appear to be associated with cache exceeding configured maximum (49 GB in cache vs 46 GB configured)


 Comments   
Comment by Sulabh Mahajan [ 15/Jul/16 ]

This issue can't be reproduced after the fix for WT-2026. So I am marking it as gone away.

Comment by Sulabh Mahajan [ 15/Jul/16 ]

I don't see this problem with the latest wiredtiger/develop.
YCSB run attached has no stalls, and max page size at eviction is as expected.

Comment by Alexander Gorrod [ 13/Jul/16 ]

sulabh.mahajan I believe this is fixed by the change in WT-2026, could you test the configuration in this ticket to confirm?

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