14_page_replacement_algorithms_II

Memoryischeappagetablescouldgethugewith

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ced during the last Τ memory accesses are the working set   Τ is called the window size 1
page
fault
=
10ms
 10ms
=
2M
instruc@ons
 T
needs
to
be
a
lot
bigger
than
2
million
 instruc@ons
 Time Requests 0 1 c 2 c 3 d 4 b 5 c 6 e 7 c 8 e 9 a 10 d Pages in Memory   What if Τ is too small? too large? • 1 t= - - t• 2 = t• 3 = • F • • • • • - • • • - F • • - • • • - • • • F • • • • • F • • • - • F • • • • • • Page a Page b Page c Page d Page e Faults What
if
T
is
too
big?
 What
if
T
is
too
small?
 19 5
 3/7/12
 Thrashing
 Load
Control
 •  Thrashing
occurs
when
the
memory
is
over‐ commiWed
and
pages
are
tossed
out
while
they
 are
s@ll
in
use
 •  Many
memory
references
cause
pages
to
be
 faulted
in
 –  Very
serious
and
very
no@ceable
loss
of
performance
 How
do
we
limit
thrashing
in
a
mul@programmed
 system?
 Load
Control
 Ready Suspended suspended
 queue
 ready
 queue
 ?
 
 Running Physical Memory –  Processes
are
swapped
out
to
disk
 Another
Note:
Page
Sizes
 Page
sizes
are
growing
slowly
but
steadily.

W...
View Full Document

Ask a homework question - tutors are online