Dear Wizards,
How can I optimise memory usage on my 3300AXP ?
I have 64 M installed on this machine which is used as
a personal workstation to support in-house applications
on a variety of machines , including other VMS boxes.
I run DECnet , TCP/IP , X.25 in the background, along
with a few print queues. DECterms are used to access
remote hosts, typically 4-8 terminals.
I know that AXP technology uses a lot more memory , but
I suspect that I can make better use of what I have.
Even with 64M installed , I can still have several
processes swapped out.
What really kills it is when I want to run Softwindows
( We really wanted to have dual boot VMS/WNT machines
but the 150 was not released when we bought the 3300s)
Many Thanks,
Swapped out processes is not a bad thing. They had to have been fairly idle to
get swapped out in the first place. If they do anything they'll be swapped back
in. The real trouble comes when processes thrash, swapping in and out, again
and again. You might be able to determine just how much swapping in and out is
going on by using the monitor utility. I think the MONITOR STATES /ALL function
would be most useful.
Typically, long before swapping becomes a big problem, the system will be
paging, especially hard faulting, a lot. Be on the look out for this.
I have a DEC 3000 model 500. Originally, I had 128MB and experienced only a
little outswapping. Now I have 320MB and have boosted the virtual cache. 64MB
does seem a little small, perhaps an upgrade would be in order?
Do you make use of AUTOGEN regularly? It will help optimize memory usage.
Alpha uses more memory for instructions for two reasons; 1) it takes more RISC
instructions to get the job done as compared to VAX; 2) the modern compilers are
more aggressive at unrolling loops. In my experience a factor of x2 or x3 is to
be expected. Alpha also tends to use more memory for data. The primary cause
of this is bigger/more buffers to minimize I/O. Secondarily, data is aligned to
natural boundaries. There is another effect Alpha has on virtual memory. This
is due to the relatively large page size. At 8KB (and 64KB for staticly linked
image sections) considerably more virtual memory may be idle. This does have an
effect on physical memory which depends heavily upon application details. Lots
of 1 byte global sections didn't hurt so bad on VAX, only wasting 511 bytes per
section. The same approach on Alpha wastes 8191 bytes physical and as much as
65,535 bytes virtual on current models. Thankfully noone (that I know of) ever
uses 1 byte sections.
DEC SoftWindows/SoftPC for OpenVMS AXP - Version 5.0 uses software to emulate
the Intel x86 instruction set. This is fine for the occasional use but
prohibitive for anything more. If what you want to do it run Intel binaries all
day long get an Intel-based system. Digital has many excellent examples
available. If what you want is run both Intel and Alpha images all day long
then consider client/server. Perhaps eXcursions would be useful.
