Very low memory usage of mongo (average 70mb)

[Rémi DESPELCHIN]

Hi!

First of all, sorry for my english :) 

I have a problem with some queries which take ~1200ms to execute and returns just a count of 600.000 lines (total lines ~3.000.000).

ex : db.pushes.find({psh:144, de:{$eq:null}}).count()

I have 5 indexes and the total amount of these indexes take 300mb

During the execution of these queries, the CPU load up to +10% by query, but the RAM usage of mongod.exe remains at a very low value : ~70mb (free memory : ~4gb).

I try to use .hint( {My index} ) to precise the index to use and put it into RAM => I got the good result, but the same execution time and the but the RAM usage of mongod.exe remains at 70mb

or

Use the "touch" command line to put all indexes of the collection into RAM  => Success, but the RAM usage of mongod.exe remains at 70mb

Please help me, I'm looking for two days the reason but unsuccessfully :(

Server

OS : Windows Server 2012 64 bits

CPU : Intel Xeon E5-2667 v2

RAM : 16gb

HDD : 100gb free

Mongo

Version : 3.0.2

StorageEngine : mmapv1

Thanks!

Kind Regards

Rémi

[Wan Bachtiar]

I have a problem with some queries which take ~1200ms to execute and returns just a count of 600.000 lines (total lines ~3.000.000).
ex : db.pushes.find({psh:144, de:{$eq:null}}).count()
I have 5 indexes and the total amount of these indexes take 300mb

Hi Remi

Can you provide the following information please :

• MongoDB deployment topology (standalone, replica set, or sharded cluster)
• The output of db.collection.getIndexes()
• The output of .hint() from your query.
• How did you measure the memory usage of mongod. i.e. Task Manager, RAMMap, etc

You may find the production checklist v3.0 useful. It contains recommendations that may help for your deployment. Also see Analyzing MongoDB Performance for general optimisation strategies.

Mongo
Version : 3.0.2

For general bug fixes for v3.0.x, I would recommend to use the latest stable of v3.0 which currently is v3.0.8.

Regards,

Wan.

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