14_page_replacement_algorithms_II

Whatiftistoosmall 19 5 3712 thrashing loadcontrol

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Unformatted text preview: pages referenced during the last Τ memory accesses are the working set   Τ is called the window size •  The
working
set
is:
 –  informally,
the
pages
the
process
is
using
right
now
 –  formally,
the
set
of
all
pages
that
a
process
referenced
in
 the
last
T
seconds
   Time Requests –  Pages
may
be
removed
even
when
no
page
fault
occurs
 –  Number
of
frames
allocated
to
a
process
will
vary
over
 @me
 •  Also
allows
pre‐paging.

 0 Pages in Memory •  Assume
that
recently
references
pages
are
likely
to
 be
referenced
again
soon
 •  Only
keep
those
pages
in
memory
(the
working
set!)
 Example: Working set computation, Τ = 4 references: • 1 t= - - t• 2 = t• 3 = Page a Page b Page c Page d Page e 1 c 2 c 3 d 4 b 5 c 6 e 7 c 8 e 9 a 10 d Faults 18 Working Set Page Replacement Implementation What
is
the
value
of
T?
   Keep track of the last Τ references   Example: Working set computation, Τ = 4 references:   The pages referen...
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This note was uploaded on 10/22/2012 for the course C S 372 taught by Professor Staff during the Spring '08 term at University of Texas.

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