More on swap.

[Gordon Messmer]

Aaron Konstam wrote:
> 
> Well this is an interesting article but it tells one nothing about swap
> fits into the virtual memory structure for the 2.4 kernel in this case.

No, but it does cover the "overcommit" feature of the Linux VM. 
Understanding overcommit and the requirements of fork() in a posix 
environment are critical to deciding how much swap you need.

Generally, the overcommit feature may allow some things to work better, 
but introduces some serious problems when the assumptions behind 
overcommit don't apply.  Hence, it's off by default.  If you're not 
using overcommit, then you should have considerably more swap than you 
intend to actually use.  Swapping is slow, and many people prefer to 
have very little because they believe that if they allow memory use to 
grow that large, the system will be very slow to respond.  In some cases 
they are right.  However, if you have insufficient swap, the login 
processes may not be able to fork, and you may not be able to log in and 
correct the problem.  Larger applications may be unable to fork, and use 
external helpers, even when there appears to be sufficient memory for 
the helpers.

I'm of the opinion that it's best to have plenty of swap, as previously 
discussed.