Re: running Linux with no swap space (but lots of RAM)

On 14 Oct 2007 15:55:18 GMT, phil-news-nospam@xxxxxxxx <phil-news-nospam@xxxxxxxx> wrote:


On Sat, 13 Oct 2007 03:51:30 GMT AZ Nomad <aznomad.2@xxxxxxxxxxxxxxxxxxx> wrote:
| On 13 Oct 2007 02:51:26 GMT, phil-news-nospam@xxxxxxxx <phil-news-nospam@xxxxxxxx> wrote:
|
|
|>On Fri, 12 Oct 2007 21:48:17 +0200 Rainer Weikusat <rweikusat@xxxxxxxxxxx> wrote:
|>| Wolfgang Draxinger <wdraxinger@xxxxxxxxxxxxxxxx> writes:
|>|> Rainer Weikusat wrote:
|>|>
|>|>> This implies that the kernel can never reuse memory allocated
|>|>> to dirty, but inactive pages associated with some applications.
|>|>> But unless you are reall short in diskspace, that buys nothing.
|>|>
|>|> That's not really an argument, it's more an excuse.
|>|
|>| It's a statement of fact: You are advocating to save disk space at the
|>| expense of RAM. What would be an argument was stating that this is a
|>| bad tradeoff, because disk space is much cheaper than RAM and much
|>| more unused.
|
|>I am not considering a swapless system to save disk space. I have plenty
|>of disk space and could easily give my system 256 GB of swap. But think
|>about it: what would have to be running to make use of 256 GB of swap?
|>And if it was running and needed something approaching 256 GB of swap,
|>then how would it be impacting the system?
|
|>Why I am considering a swapless system is for the speed. Instead of
|>having 4GB of RAM and 4GB of swap, I would have 8GB of RAM and no swap.
|
|>A page that is dirty and would get swapped out can instead take up RAM
|>space. Either way, it's taking a page away from that 8GB of space.
|
| And taking those pages away from usefull work as file system cache.
| Your system will in actuality be slower as you'll have to go to the
| physical disk more often.

When comparing a 4GB/4GB (RAM/swap) system to 8GB/0GB, the file system
cache isn't going to get that page either way.

Imagine if I partitioned the 8GB into 4GB of RAMdisk and made that whole
RAMdisk be my swap device. A dirty page now has to be copied from the
4GB of usable RAM into the 4GB of RAMdisk, and later back again.

Whenever I hear about somebody using a ramdisk as a swap, I can't help
but laugh.

Ram, simulating disk, simulating ram. Why stop there? Maybe you can put
the ramdisk on a network and slow things down some more. Perhaps you should
use a memory stick for your swap. That ought to be good for some more laughs
at slowing things to a halt.
.

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