Memory usage

[Markus Schönhaber]

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.

-- 
Regards
  mks