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Type: Bug
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Resolution: Works as Designed
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Priority: Major - P3
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None
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Affects Version/s: 3.6.7, 3.6.8
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Component/s: WiredTiger
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ALL
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Storage Engines 2018-11-19, Storage Engines 2018-12-03
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(copied to CRM)
As I said in https://jira.mongodb.org/browse/SERVER-17424?focusedCommentId=2044120&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-2044120 I noticed yet another regression in 3.6 about memory usage this time (after the secondary CPU × 4 increase and the IO usage × 5 increase), I now have almost twice the configured cacheSize used by mongo, and it increased a lot since 3.4.15:
I first upgraded to 3.6.7 and then 3.6.8 after https://jira.mongodb.org/browse/SERVER-35958?focusedCommentId=2007204&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-2007204
My configured max cache is 10G (server has 32G RAM):
rs0:PRIMARY> db.serverStatus().version
3.6.8
rs0:PRIMARY> db.serverStatus().wiredTiger.cache["maximum bytes configured"]
10737418240
And my actual usage is 19G RES (21G VIRT):
rs0:PRIMARY> db.serverStatus().tcmalloc.tcmalloc.formattedString
------------------------------------------------
MALLOC: 16556355400 (15789.4 MiB) Bytes in use by application
MALLOC: + 3597598720 ( 3430.9 MiB) Bytes in page heap freelist
MALLOC: + 227350168 ( 216.8 MiB) Bytes in central cache freelist
MALLOC: + 884736 ( 0.8 MiB) Bytes in transfer cache freelist
MALLOC: + 290449952 ( 277.0 MiB) Bytes in thread cache freelists
MALLOC: + 67035392 ( 63.9 MiB) Bytes in malloc metadata
MALLOC: ------------
MALLOC: = 20739674368 (19778.9 MiB) Actual memory used (physical + swap)
MALLOC: + 1484984320 ( 1416.2 MiB) Bytes released to OS (aka unmapped)
MALLOC: ------------
MALLOC: = 22224658688 (21195.1 MiB) Virtual address space used
MALLOC:
MALLOC: 286938 Spans in use
MALLOC: 886 Thread heaps in use
MALLOC: 4096 Tcmalloc page size
------------------------------------------------
Here is the full serverStatus: server_status.json
- related to
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SERVER-37926 Excess allocated memory associated with cursors due to WT "modify" operations
- Closed
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WT-4418 Don't keep key/value memory buffers allocated for cached cursors
- Closed