MongoDB MEM Management

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NEVER USE MONGODB ON PRODUCTION.

Here the guy also meet my problem: https://news.ycombinator.com/item?id=5704572

This post is about MongoDB memory management mechanism.
All it’s using is Page Cache of System.

This is a good experience report: https://speakerdeck.com/mitsuhiko/a-year-of-mongodb

This URL gives you more details
https://www.mongodb.com/presentations/mongodb-memory-management-demystified

OK, this post is just for me to check commands to use, to management MongoDB.

1. connect

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mongo 127.0.0.1:20001/${DB_NAME} -u ${USER_NAME} -p ${PASSWORD}

2. db working set

Use this to determine how much memory do you need of your working set under your current database.

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> > db.runCommand({serverStatus: 1, workingSet: 1}).tcmalloc.formattedString
------------------------------------------------
MALLOC:     7614540648 ( 7261.8 MiB) Bytes in use by application
MALLOC: +    236527616 (  225.6 MiB) Bytes in page heap freelist
MALLOC: +    657428112 (  627.0 MiB) Bytes in central cache freelist
MALLOC: +     53399376 (   50.9 MiB) Bytes in transfer cache freelist
MALLOC: +     17635000 (   16.8 MiB) Bytes in thread cache freelists
MALLOC: +     27570336 (   26.3 MiB) Bytes in malloc metadata
MALLOC:   ------------
MALLOC: =   8607101088 ( 8208.4 MiB) Actual memory used (physical + swap)
MALLOC: +    603160576 (  575.2 MiB) Bytes released to OS (aka unmapped)
MALLOC:   ------------
MALLOC: =   9210261664 ( 8783.6 MiB) Virtual address space used
MALLOC:
MALLOC:         326169              Spans in use
MALLOC:             56              Thread heaps in use
MALLOC:           8192              Tcmalloc page size
------------------------------------------------
Call ReleaseFreeMemory() to release freelist memory to the OS (via madvise()).
Bytes released to the OS take up virtual address space but no physical memory.

3. db.stats()

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> db.stats()
{
	"db" : "xxxx", // this has been covered due to classification info 
	"collections" : 4,
	"objects" : 39817003,
	"avgObjSize" : 113.20676571262784,
	"dataSize" : 4507554130,
	"storageSize" : 2112126976,
	"numExtents" : 0,
	"indexes" : 12,
	"indexSize" : 2265329664,
	"ok" : 1
}
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