[SERVER-24970] Allow For Cache Sizes In MBs, from Config File Created: 09/Jul/16  Updated: 14/Jul/16  Resolved: 10/Jul/16

Status: Closed
Project: Core Server
Component/s: WiredTiger
Affects Version/s: 3.2.7
Fix Version/s: None

Type: Bug Priority: Minor - P4
Reporter: Antonio Malcolm Assignee: Unassigned
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Duplicate
duplicates SERVER-23624 Allow wiredTigerCacheSizeGB to be spe... Closed
Related
Operating System: ALL
Participants:

 Description   

Currently, to set the WiredTiger cache size in MBs, rather than GBs, we're forced to do so via a commandline option (which isn't listed in the docs, or via mongod --help). This makes the assumption that nearly everyone using MongoDB has or needs large server requirements to work with, and ignores users who run services/sites/application from smaller setups (in particular, VMs).

Also, as mentioned, the command arg to limit the size to MBs isn't listed, and I found it on the mongodb-user google group page:

https://groups.google.com/forum/#!msg/mongodb-user/V2Q4LZAe2m0/pqNSu4psDQAJ

Specifically: --wiredTigerEngineConfigString="cache_size=xxxM"



 Comments   
Comment by Ramon Fernandez Marina [ 10/Jul/16 ]

antonio-malcolm, please see this comment explaining how to set the cache size in MBs in the config file.

Regards,
Ramón.

Comment by Daniel Pasette (Inactive) [ 10/Jul/16 ]

This is fixed in SERVER-23624 and will be available in 3.4

Comment by Antonio Malcolm [ 10/Jul/16 ]

Well, I just answered my own question:
Error parsing option "storage.wiredTiger.engineConfig.cacheSizeGB" as int: Bad digit "." while parsing 0.25

So, your documentation is off- it needs an int, not a number. In any case, a setting lower than 1GB should be available, without resorting to an undocumented command line arg.

Comment by Antonio Malcolm [ 09/Jul/16 ]

OK, I just noticed the distinction, in the MongoDB docs, between <number>, as the value type, and <int>, with <number> used to set the cache size.

Does this mean decimal values can be used, for the cache and in-memory sizes? That would satisfy this ticket.

Also, it appears, in one of your rmore recent code changes, the use of Double was employed.... but as that was a very small subsection of your overall code base, I don't want to jump to conclusions.

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