[rescue] Spark10 CPU question

[Sandwich Maker]

" From: Dave McGuire <mcguire at neurotica.com>
" 
" 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.

that matches my understanding.

the giant spinlock seems like rather a crude hack for multiproc
support.  surely sun could've done better - but they didn't have to; i
was at another job that had a solbourne about the time they were going
under, and i thought it was a shame that their work on finer-grain
spinlocks in the sunos kernel was just landfilled [along with other
interesting things].  but sun was understandably not interested in
anything which would slow customers in moving from sunos to solaris,
especially when they were moving much slower than they wanted anyway.

"   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.

my understanding also.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh at an.bradford.ma.us                       and think what none thought