Re: RHEL 4 improvement in use of swap? (compared to RHEL 3)

[Dirk Gfroerer <Dirk Gfroerer guh-software de>]

> We saw the same behavior with RHEL3.  It preferred disk cache so much 
> that our applications would suffer greatly.
>
> One of our DB boxes has 8GB of RAM.  We fed MySQL 6GB of RAM, but found 
> that RHEL3 was keeping 4-5GB of disk cache around, and thus, would swap 
> out 2-3GB of MySQL, causing massive slowdowns.
>
> Like you, we just disabled swap and watched a free, massive performance 
> increase.
>
> We're now on RHEL4 with lots of our boxes, but I haven't had the guts to 
> enable swap on any of them.  I just make sure we buy ample RAM and never 
> need it.  I wouldn't mind having it as a safety net, if I knew the 
> prefers-disk-cache-to-application-RAM problem was fixed, though... 
> Anyone done any comparisons?
At least on my Oracle boxes the database is still being paged out (RHEL4 
U2). I've set vm.swappiness=0, but this doesn't seem to make any difference.

Dirk