working set size

[tetlika]

hi

I want to clarify the meaning of working set size which is estimated by db.runCommand( { serverStatus: 1, workingSet: 1 } ) command

so, I have next output:

"workingSet" : {

"note" : "thisIsAnEstimate",

"pagesInMemory" : 654978,

"computationTimeMicros" : 115617,

"overSeconds" : 10

},

so it means that size of my working set is estimated as 654978x4000bytes (around 2.7 Gbytes), so according to that estimation it would be enough to have around 5 Gbytes of RAM, right?

another question what does "overSeconds" mean? (on different instances I have very different overSeconds values)

thanks

[Sam Millman]

Overseconds means that the measurements was done over the period of 10 seconds.

Ideally you want to graph the 10 minute output of workingSet and see how it fluctuates to get your actual working set.

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[tetlika]

so assuming that during 10 minutes the working set is around 654978 all the time,so does it mean that I need around 5Gbytes of ram?

thanks

Пʼятниця, 17 січня 2014 р. 10:06:46 UTC+2 користувач Sammaye написав:

[Sam Millman]

I would make it 10GB to be safe, but yes, it is a good rough estimation.

[Adam Winn]

Overseconds actually means the delta between the oldest and newest pages tracked in pagesInMemory at that time. A small value implies that the working set is close to or greater than the available memory size. A large value implies that the working set is smaller than the available memory size. 

Ref: http://docs.mongodb.org/manual/reference/command/serverStatus/#serverStatus.workingSet.overSeconds

[Sam Millman]

> overSeconds returns the amount of time elapsed between the newest and oldest pages tracked in the pagesInMemory data point.

from the page you just reference

For other MongoDB technical support options, see: http://www.mongodb.org/about/support/.

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