On Fri, 2005-02-11 at 00:53 +0000, James Wilkinson wrote:
> Why does the disk spin and the machine lock up when it hits swap? If
> the memory is cache, then surely it won't start swapping until the
> cache memory is utilised.
Does it just go very very slowly, or does it completely freeze? As if
it's freezing, then I'd suspect that there is something odd with that
swap file. You could always try booting into single user mode, use
swapoff -a to stop Linux using it, and mkswap to recreate it.
Normally, Linux *will* start using swap before it has exhausted its
cache, simply because there will be parts of some files that will be
accessed more often than parts of some program memory.
But normally, you should hardly notice light swap usage.
If Linux doesn't completely freeze, then you might like to watch the top
command and see how CPU time switches between "us" (user mode: normal
programs), "sy" (kernel mode: mainly dealing with disks, filesystems and
hardware), "wa" (waiting for hard disks, etc.) and "id" (idle time).
That might give you pointers.
Could this be what I have been experiencing? I had to shutdown readahead
and readahead_early to keep FC3 from loading up RAM and then locking me
out of the system while it decided to write dirty pages to disk. From
what little I know about this, I need to tweak the configuration files
in /proc/sys/vm/ to come up with a happy medium. Shutting down the
'readahead twins' seemed to have settled things down...for now. I'm
hoping to find someone here that has already looked at these files and
has an idea what I can be done with them. Anyone?