Solución de los ejercicios de memoria virtual

NRU

Acceso
  a        1(R)  3(R)  3(W)  3(R)  4(R)  5(R)  1(R)  2(W)  5(W)  1(W)  3(R)  4(R)
página
         +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
         |  1  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |
Marco 1  | R=1 |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |
         | M=0 |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  | M=1 |  =  |  =  |
         +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
         |     |  3  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |
Marco 2  |     | R=1 |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |
         |     | M=0 | M=1 |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |  =  |
         +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
         |     |     |     |     |  4  |  =  |  =  |  2  |  =  |  =  |  =  |  4  |
Marco 3  |     |     |     |     | R=1 |  =  |  =  | R=1 |  =  |  =  |  =  | R=1 |
         |     |     |     |     | M=0 |  =  |  =  | M=1 |  =  |  =  |  =  | M=0 |
         +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
         |     |     |     |     |     |  5  |  =  |  =  |  =  |  =  |  =  |  =  |
Marco 4  |     |     |     |     |     | R=1 |  =  |  =  |  =  |  =  |  =  |  =  |
         |     |     |     |     |     | M=0 |  =  |  =  | M=1 |  =  |  =  |  =  |
         +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
Fallo    |     |     |     |     |     |     |     |     |     |     |     |     |
 de      |  x  |  x  |     |     |  x  |  x  |     |  x  |     |     |     |  x  |
página   |     |     |     |     |     |     |     |     |     |     |     |     |
         +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+

Tiempo      1     2     3     4     5     6     7     8     9    10    11    12

                            nº fallos de página     6
Tasa de fallos de página = --------------------- = ---- = 0,5
                            nº accesos a páginas    12

Sustitución por envejecimiento

Periodo de 4, registro R de 3 bits, desempate: LRU

    _________________accesos a página__________________
    |_2_|_3_|_3_|_1_||_4_|_5_|_4_|_1_||_5_|_2_|_3_|_4_|
 ======================================================
  1 | 2 | = | = | = || 2 | 5 | = | = || 5 | = | = | = |
    |100| = | = | = ||010|100| = | = ||110| = | = | = |
m---|---|---|---|---||---|---|---|---||---|---|---|---|
a 2 |   | 3 | = | = || 3 | = | = | = || 3 | 2 | = | = |
r   |   |100| = | = ||010| = | = | = ||001|100| = | = |
c---|---|---|---|---||---|---|---|---||---|---|---|---|
o 3 |   |   |   | 1 || 1 | = | = | 1 || 1 | = | = | 4 |
s   |   |   |   |100||010| = | = |110||011| = | = |100|
 ---|---|---|---|---||---|---|---|---||---|---|---|---|
  4 |   |   |   |   || 4 | = | = | = || 4 | = | 3 | = |
    |   |   |   |   ||100| = | = | = ||010| = |100| = |
 --------------------------------------------------------> t
      x   x       x    x   x                x   x   x

                    8
 tasa fallos pág = ---- 
                    12