psudo-LRU(Tree LRU) 的实现

最新推荐文章于 2025-05-20 15:25:14 发布

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最新推荐文章于 2025-05-20 15:25:14 发布 · 5.3k 阅读

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#tree #reference #encoding #branch #input #cache

本文详细介绍了如何使用3位LRU位r0，r1，r2实现一组4行L0，L1，L2，L3的pseuso-LRU策略。通过设置不同的标志位，确定最近访问的行，并据此规则进行缓存替换操作。在清洗或复位时，所有LRU位将被清零。

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pseudo-LRU

two-way set associative - one bit

   indicates which line of the two has been reference more recently


four-way set associative - three bits

   each bit represents one branch point in a binary decision tree; let 1
   represent that the left side has been referenced more recently than the
   right side, and 0 vice-versa

              are all 4 lines valid?
                   /       /
                 yes        no, use an invalid line
                  |
                  |
                  |
             bit_0 == 0?                                state | replace      ref to | next state
              /       /                                         ------+--------        -------+-----------
             y         n                                       00x  |  line_0      line_0 |    11_
            /           /                                       01x  |  line_1      line_1 |    10_
     bit_1 == 0?    bit_2 == 0?                   1x0