Re: Swap Memory

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Thu, 5 Feb 2009 12:40:31 -0800
William Chan <williamchan@google.com> wrote:
> > That could be changed, yes: but would multiply the amount of memory
> > needed for recording pages out of swap.  The present design is to
> > minimize the memory needed by what's out on swap.
> 
> Hopefully there will be less pages in swap than in system memory. If
> this is true - the overhead introduced should be minimal relative to
> the overhead the kernel already has for manging system memory pages.
> 
In my experience, you can't assume that ;)

BTW, if you want to do that, changing device layer is much easier than changing
memory management layer. 

Maybe adding device mapper for good-scheduled-swap(but not Raid0) is enough.
Preparing device-mapper layer which does
  1. It can tie several devices of different size.
  2. It chases each block's usage by some logic (LRU) and do block migration
     if necessary.
  3. priority between devices can be set by dm's user-land tools.

Hmm? But I'm not sure this is worth tring.

Thanks,
-Kame

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