Xref: utzoo comp.arch:11089 comp.sys.mips:105
Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!unisoft!cander
From: cander@unisoft.UUCP (Charles Anderson)
Newsgroups: comp.arch,comp.sys.mips
Subject: Re: Memory utilization & inter-process contention
Message-ID: <2394@unisoft.UUCP>
Date: 23 Aug 89 18:00:58 GMT
References: <3332@blake.acs.washington.edu>
Lines: 32

From article <3332@blake.acs.washington.edu>, by lgy@blake.acs.washington.edu (Laurence Yaffe):
> Questions:
>     Which (if any) high-performance Unix systems are capable of avoiding
> this type of inter-process contention?  What works best - actual process
> swapping layered on top of demand paging, better paging algorithms,
> clever scheduling based on adaptive process priorities, ... ?

Straight out of school  I worked on a proprietary, non-Unix system that
handled this problem fairly well (even though the company went out of
business).  In addition the usual queues for runable procs, I/O waiting
procs, etc, the operating system had a "trouble maker" queue.  This was
for processes that were making too many demands on the system, i.e.
encouraging thrashing.  Processes on the TM queue were stripped of
their resources (essentially swapped out, I think).  After a while they
were allowed to return and were given some extra grace because the
first thing they're going to do is page-fault in their working set
which would otherwise land them right back in the pokey.

In the example that Mr. Yaffe gives, there would be two processes, A &
B, competing with one another and thus driving the system towards
thrashing.  The system sees this, selects A as the trouble maker and
puts him in the penalty box.  B runs fine without A getting in his
way.  After a while A is allowed to return and he starts slamming
against B.  A is graced, having just returned from the TM queue, so B
gets selected for the TM queue and A runs well until B returns when the
sequence repeats again.  I don't know how well this would work on a real 
Unix system, but it seemed to work well for this particular system.  

-- 

Charles.
{sun, amdahl, ucbvax, pyramid, uunet}!unisoft!cander