Question regarding inactive memory

Question regarding inactive memory

[David van Hoose]

This may be a bit of a newbie'ish question, and maybe a bit off-topic, 
but is there any way for me to remove inactive memory, either explicitly 
or implicitly? I have 512MB of PC2700 SDRAM, but my system is constantly 
eating into the swap I have on my system since I have usually about 
140-300MB of inactive (and dirty) RAM and usually about only 250MB in 
active memory. Is there a way for me to correct this bad memory usage 
without having to reboot? If patching the kernel would be a possible 
route to venture to, I'm game.

Any suggestions or comments are welcome.

Thank you all!
David

Re: Question regarding inactive memory

[Richard B. Johnson]

On Tue, 29 Apr 2003, David van Hoose wrote:

> This may be a bit of a newbie'ish question, and maybe a bit off-topic,
> but is there any way for me to remove inactive memory, either explicitly
> or implicitly? I have 512MB of PC2700 SDRAM, but my system is constantly
> eating into the swap I have on my system since I have usually about
> 140-300MB of inactive (and dirty) RAM and usually about only 250MB in
> active memory. Is there a way for me to correct this bad memory usage
> without having to reboot? If patching the kernel would be a possible
> route to venture to, I'm game.
>
> Any suggestions or comments are welcome.
>
> Thank you all!
> David
>

Assuming you are not using a development kernel, the memory
manager will try to use most all available RAM. This is
normal. During most usage, many of the daemons get swapped out,
and unless they are awakened, they don't get swapped back in.
This is normal because one does not want to waste the CPU
cycles necessary to swap back in RAM data that will not be
used.

The purpose of using most all available RAM is to save CPU
cycles and make the machine responsive. If you have a program
that needs RAM, it is grabbed from those buffers you see if
you do `cat /proc/meminfo`. The idea is to nat waste any
RAM.

If you want to just write the stuff on your swap device(s)
back to RAM, to see that it "really works", just execute,
`swapoff -a` as root. You can then execute `swapon -a` and
you are back to "normal".

The 'dirty' buffers are kept around, even after being written
to disk, so they don't have to be re-read the next time you
execute `ls` or run a program.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.

Re: Question regarding inactive memory

[David van Hoose]

Richard B. Johnson wrote:
> On Tue, 29 Apr 2003, David van Hoose wrote:
> 
> 
>>This may be a bit of a newbie'ish question, and maybe a bit off-topic,
>>but is there any way for me to remove inactive memory, either explicitly
>>or implicitly? I have 512MB of PC2700 SDRAM, but my system is constantly
>>eating into the swap I have on my system since I have usually about
>>140-300MB of inactive (and dirty) RAM and usually about only 250MB in
>>active memory. Is there a way for me to correct this bad memory usage
>>without having to reboot? If patching the kernel would be a possible
>>route to venture to, I'm game.
>>
>>Any suggestions or comments are welcome.
> 
> Assuming you are not using a development kernel, the memory
> manager will try to use most all available RAM. This is
> normal. During most usage, many of the daemons get swapped out,
> and unless they are awakened, they don't get swapped back in.
> This is normal because one does not want to waste the CPU
> cycles necessary to swap back in RAM data that will not be
> used.
> 
> The purpose of using most all available RAM is to save CPU
> cycles and make the machine responsive. If you have a program
> that needs RAM, it is grabbed from those buffers you see if
> you do `cat /proc/meminfo`. The idea is to nat waste any
> RAM.
> 
> If you want to just write the stuff on your swap device(s)
> back to RAM, to see that it "really works", just execute,
> `swapoff -a` as root. You can then execute `swapon -a` and
> you are back to "normal".
> 
> The 'dirty' buffers are kept around, even after being written
> to disk, so they don't have to be re-read the next time you
> execute `ls` or run a program.

I am currently using kernel 2.4.21-rc1.
Problem I am having is that my swap is used only after all of my 
physical ram is used. My system then starts to run a lot slower. 
Especially processes that allocate lots of memory. If the kernel knows 
that memory is inactive, why doesn't it swap it to disk so that memory 
doesn't have to be shuffled around when a new process needs memory? It 
would also make me happy to be able to swap dirty memory to disk.

Thanks,
David