linux memory mgmt system question

linux memory mgmt system question

[Catalin CIONTU]

> Hi,
> 
> 1. Firstly, we want to know if 'free' is the best
> tool that could give us the most accurate numbers with re to
> used/free memory and swap. If not, what would be that tool
> we could rely on?
> 2. Are there any exceptions that may "fool" free
> utility (inaccurate numbers would be returned), that we
> would need to be aware of? For example, could things like
> huge TLB pages being enabled have an impact on the numbers
> reported by free utility?
> 
> Could you please advise? Thanks a lot.
> 
> 
> Regards,
> catalin.


      

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Re: linux memory mgmt system question

[Christoph Lameter]

The numbers returned by free are numbers that describe the state of the
memory for the OS. The OS can increase the amount of free memory at
any time by reclaiming memory from the disk cache, processes and other
operating system structures.

Why do you need these numbers?

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Re: linux memory mgmt system question

[Catalin CIONTU]

Hi,

Thanks for your reply. 

We need to provide these numbers for our customers, when we release reports of findings and assessments. The more accurate they are, with re to memory utilization, the better. They'll setup thresholds for their monitoring tools, based on our feedback.


Regards,
catalin.
--- On Fri, 11/21/08, Christoph Lameter <cl@linux-foundation.org> wrote:

> From: Christoph Lameter <cl@linux-foundation.org>
> Subject: Re: linux memory mgmt system question
> To: "Catalin CIONTU" <cciontu@yahoo.com>
> Cc: linux-mm@kvack.org
> Date: Friday, November 21, 2008, 6:29 PM
> The numbers returned by free are numbers that describe the
> state of the
> memory for the OS. The OS can increase the amount of free
> memory at
> any time by reclaiming memory from the disk cache,
> processes and other
> operating system structures.
> 
> Why do you need these numbers?


      

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Re: linux memory mgmt system question

[Christoph Lameter]

On Fri, 21 Nov 2008, Catalin CIONTU wrote:

> We need to provide these numbers for our customers, when we release
> reports of findings and assessments. The more accurate they are, with re
> to memory utilization, the better. They'll setup thresholds for their
> monitoring tools, based on our feedback.

The VM manages thresholds for many of these counters. Interpretation of
what they mean may be difficult.

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Re: linux memory mgmt system question

[Tim Pepper]

On Thu, Nov 20, 2008 at 6:15 AM, Catalin CIONTU <cciontu@yahoo.com> wrote:
>> Hi,
>>
>> 1. Firstly, we want to know if 'free' is the best
>> tool that could give us the most accurate numbers with re to
>> used/free memory and swap. If not, what would be that tool
>> we could rely on?
>> 2. Are there any exceptions that may "fool" free
>> utility (inaccurate numbers would be returned), that we
>> would need to be aware of? For example, could things like
>> huge TLB pages being enabled have an impact on the numbers
>> reported by free utility?
>>
>> Could you please advise? Thanks a lot.

There is a lot of room for confusion and being fooled into wrong
conclusions in this space.  As per Christoph, it would be
interesting/helpful to know more about what you're trying to figure
out.

You might want to have a look at this wiki faq (and some of the other
pages on that wiki):
http://linux-mm.org/Low_On_Memory



Tim

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