Article View: comp.arch
Article #2037Re: Working Set replacement, use bits (was re: memory utilization...)
From: John Hascall
Date: Tue, 29 Aug 1989 14:04
Date: Tue, 29 Aug 1989 14:04
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1595 bytes
In article <11564> wilson@carcoar.Stanford.EDU (Paul Wilson) writes:
} An explanation of WS:
}The basic idea of the Working Set policy is that each process gets
}to keep in memory all of the pages that it has referenced within
}some period of time T. For any given process, the Least Recently Used
}(LRU) page is always evicted. What makes it different from normal
}LRU is that the amount of memory allocated to a process is variable --
}it is any number of pages referenced within the last T units of time.
}(T units of the given process' execution time that is.)
It has been a while since I looked at this, so my memory could be
a little moldy...
I believe that when designing the WS scheme for VMS they studied
various replacement algorithms (LRU, FIFO and RANDOM) and found
that RANDOM was just about as effective as the other two. It also
has the virtue of being easier to implement.
Does VMS, in fact, still use random replacement?
John Hascall
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arc1-ca.pugleaf.net!utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!uxc.cso.uiuc.edu!dino!atanasoff!hascallReferences:
<11564@polya.Stanford.EDU>Show Full Headers
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Path: arc1-ca.pugleaf.net!utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!uxc.cso.uiuc.edu!dino!atanasoff!hascall From: hascall@atanasoff.cs.iastate.edu (John Hascall) Newsgroups: comp.arch Subject: Re: Working Set replacement, use bits (was re: memory utilization...) Keywords: working set, replacement, virtual memory, use bits Message-ID: <1402@atanasoff.cs.iastate.edu> Date: 29 Aug 89 14:04:26 GMT References: <11564@polya.Stanford.EDU> Reply-To: hascall@atanasoff.cs.iastate.edu.UUCP (John Hascall) Organization: Iowa State Univ. Computation Center Lines: 23