[rescue] Spark10 CPU question

[Dave McGuire]

On 12/14/2016 02:43 PM, Sandwich Maker wrote:
> " From: john ferguson <jferg977 at aol.com>
> " 
> " 
> " I'm running an old (but great)  CAD program on an SS10 using SunOS 
> " 4.1.4.  I also have a SPARCPrinter 1, which also works and have compiled 
> " a 2006+/- flavor of Ghostscript to accept more modern versions of 
> " PostScript output and print them.  And, no, I didn't really know what I 
> " 
> " []
> " 
> " to the question:
> " 
> " My memory is that there is no benefit for multiple processors in 4.1.4, 
> " and it seems unlike the application I use the most would benefit either.
> 
> there is, for heavy cpu-pig apps like cad, even if they're
> single-threaded and under sunos4's primitive 'multiproc' - the app can
> substantially hog only one cpu, but that leaves the other free to do
> everything else a running system wants.
> 
> i saw this at a network-gear shop in the mid '90s; workstations with
> only one proc were virtually unusable while doing sims, but ones with
> dual procs were only a little slowed in the logic editor by the
> 'background' task.  sims went faster too, since they were swapped less
> with their 'own' cpu.

  The big issue here is, as I understand it, is the lack of fine-grained
locking in SunOS4.  There's one big lock going into kernel space, so
only one processor can execute code in kernel space at a time.  Solaris
has very VERY fine-grained locking, so lots of processes/threads can be
running around in the kernel simultaneously.  In fact, if memory serves,
each instance of a device driver also gets its own thread in Solaris,
making things even smoother when there are lots (dozens) of processors
involved.

  How much of a performance benefit you get from multiple processors
really depends on the workload, and how much of it involves heavy
processing in user space vs. making frequent calls to the kernel for
I/O, etc.

              -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA