Memory usage

[Billie Walsh]

On 11/29/2010 08:53 AM, Mark Syms wrote:
>> Message: 6
>> Date: Mon, 29 Nov 2010 14:15:29 +0100
>> From: Markus Sch?nhaber<ubuntu-users at list-post.mks-mail.de>
>> Subject: Re: Memory usage
>> To: ubuntu-users at lists.ubuntu.com
>> Message-ID:<4CF3A771.901 at list-post.mks-mail.de>
>> Content-Type: text/plain; charset=ISO-8859-1
>>
>> 29.11.2010 13:37, Billie Walsh:
>>
>>      
>>> On 11/28/2010 11:41 PM, Cristopher Thomas wrote:
>>>        
>>      
>>>> Over the past week I've tried disabling a few different applications
>>>> that I thought likely culprits.  Gnome Do, Zeitgeist, offlineimap,
>>>> Dropbox... Still no luck.
>>>>
>>>> Oddly enough, I've also noticed that swap isn't being used at all,
>>>>          
> which
>    
>>>> seems weird.
>>>>          
>>> I could be wrong, and I'm sure that if I am someone will correct me. If
>>>        
>    
>>> I remember correctly your OS will use memory to the maximum amount
>>> available before it uses swap. If you have sufficient memory to run
>>> whatever applications are open it will show the memory maxed out and
>>> nothing in swap.
>>>        
>> Well, your statement is a bit too general. From man 5 proc:
>> | /proc/sys/vm/swappiness
>> |    The  value in this file controls how aggressively the kernel
>> |    will swap memory pages.  Higher values increase agressiveness,
>> |    lower values descrease aggressiveness.  The default value is 60.
>>
>> So, you can manipulate the kernel's behaviour wrt to swapping by writing
>> to /proc/sys/vm/swappiness or changing the corresponding sysctl variable
>> vm.swappiness. IAW there's no absolutely fixed point wrt to memory load
>> when the kernel starts swapping.
>>
>> LWN has an article about this topic:
>> http://lwn.net/Articles/83588/
>> Although old, I guess it still presents the general idea correctly.
>>
>> That said, if taken as a rule of thumb like "the more RAM available, the
>> less likely it is for the kernel to swap", your statement above points
>> in the right direction.
>>      
> Indeed, which is why if you run the 'free' command from a terminal the
> second line is "-/+ buffers/cache" and this shows how much "free" memory
> is being consumed in buffering and caching data read from disk. If this
> memory
> is needed for running applications the buffers and caches get flushed and
> the requried space allocated to the applications. My home server shows 77M
> free but
> 496M after discounting buffers and cache.
>
> HTH,
>
> Mark.
>
>    

Memory allows faster access to "data" than disks.

-- 
"A good moral character is the first essential in a man." George Washington

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