[X-Unix] syslogd problems

[Kevin Stevens]

On Wed, 9 Jun 2004, James Bucanek wrote:

> Inactive memory can exist in several states.  Inactive+allocated means
> that the memory block is mapped into a process's memory space, but
> simply hasn't been accessed in awhile.  Thus the term "inactive" rather
> than "unused."  These blocks can not be simply discarded.  They belong
> to some app and contain data.  These are typically the first candidates
> for blocks that will be swapped out if new blocks are needed.
>
> The kernal periodically sweeps the list of active blocks and marks those
> as inactive that haven't been touched in awhile.  It has an algorithm
> that tries to maintain an optimal balance between active and inactive
> blocks.
>
> Inactive+unallocated are used as temporary cache.  These can contain
> previously loaded code, disk buffers, whatever.  The idea is that the
> kernel knows what's in these blocks and can instantly resurrect them if
> the need arises.  These blocks do not have to paged out to be reused.
>
> What can be confusing is that most of the system status utility simply
> list the total amount of "inactive" memory, without regard to what kind
> or combination of "inactive" it is.  You'll often notice the number of
> inactive blocks jump up or down as a consequence of a process touching a
> bunch of memory, or after not touching it for awhile.

I think I'd better stick to networking.  ;)

> >Or why I need 3+ GB of swap in the first place, or why after allocating
> >all that "base" swap it needs to add another 74MB swap file.
>
> Probably because it ran out of real RAM and some process asked for more.
> This happens quite often. ;)

Yeah, I'm calling 'shenanigans'.  This same OS version runs on an iBook
with 256MB of ram and half the VM, but when it is loaded on a G5 with
1.5GB, just the applications that run on system startup require almost 5GB
of VM?  Yet after running Photoshop and other memory intensive apps, it
hasn't increased any further?  I'm sorry, I just don't buy it.  There's
gotta be some automatic sizing and automatic swap file creation stuff
going on without regard to actual memory use.

Shenanigans!

KeS