Slide 7
Slide 7 text
An Performance
5,3 I=B Ulbih In/PL
an
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In/PE 18 an enhanceaent to In which reduces overhead for the I=R
virtual nachine, priaarily by allowing it to run in real supervi-
sor state, thereby eliminating the siaulation or lost privileged
operations. Another advantage oi In/P2 is the ability to with-
stand CP crashes: In/PE gives control to the I=R virtual nachine
when CP crashes; the V=R aachine can later restart CP without
disrupting its own operation,
there are a nuwber of aajor problems with running under VB/PE,
Since real storage is consumed in I=R operation,
it would
still
he necessary to iapleaeut paging, llso, since lu would run in
real supervisor state, a kernel error in Au could crash the
entire Uh systen. Two problems arise because bu under In/PE
would have to continue to run
if CP crashes, One, aachine check
recovery and recording would be necessary (more on this later),
Two, all oi Lu's devices would have to be real devices, so sane
l/0 tleribility would be lost (no ninidisk I/0, no virtual CPCA
coswunication, etc,). finally, I!/PE itselt nay need slight
wodiiications, since
it was designed only to support IVS.
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The advantages of running Lu on
its own are fairly obvious: the
control oi the resources oi an entire nachine and the indepen-
dence ot operation iron other systems. the disadvantages are not
all so obvious, As with In/PE, paging and machine check handling
would have to he inplewented, But the big problen arising tron
stand-alone operation is the loss oi coawunication with other
systess. Cowwunications drivers andlor shared disk access tech-
niques would need to he developed to regain access to these
foreign systews, Ot course, an obvious deterrent to stand-alone
operation is the hardware, maintenance, and operations cost,
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II Au runs as the V=B
virtual nachine (including In/PE), then the
nvs system currently running there will be displaced. In normal
operation, the only purpose or this SIS systen is to allow the
other virtual aachines to coawunicate with BVS on the other real
nachines, This function could be replaced by BVS running in a
normal virtual machine, or, aore likely, by the V! RSCS program
product. However, when either systen C or D
is down, the CCS
backup plan calls for running both va and production BIS (under
In/FE) on the reaaining CPU, In this situation, it seess
unlikely that Au would be allowed to reaain in the V=R area;
it
would revert to running as a normal virtual aachine.
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a n d a h 1 Software P/I 510511-700 Rev A Page 7
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