Limiting program swap

[Bill Davidsen <davidsen@tmr.com>]

I have several machine of various memory sizes which suffer from really 
poor performance when doing backups. This appears to be because all the 
programs other than the backup quickly get swapped to make room for i/o 
buffers.

Is there some standard portable way to prevent this, either by reserving 
some memory for programs which will not get swapped regardless of i/o 
pressure, or alternatively limiting the total memory used for i/o 
buffers, dcache, and similar things?

I did a crude hack for 2.4.17, but if I'm missing some obvious trick I'd 
rather not do something which can't go in the mainline kernel. Anyone 
care to show me what I missed, or is this just a characteristic of Linux?

-- 
    -bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
  last possible moment - but no longer"  -me