TiVaPRoMi: Time-Varying Probabilistic Row-Hammer Mitigation

Row-Hammering is a challenge for computing systems that use DRAM. It can cause bit flips in a DRAM row by accessing its neighboring rows. Several mitigation techniques on memory controller level were already suggested. The techniques are in two categories: The first category uses static probabilities, which leads to a performance penalty due to a high number of extra row activations. The second category is based on so-called Tabled Counters, which have large hardware requirements and are mostly infeasible to implement. We introduce a novel Row-Hammer mitigation technique that uses time-varying probabilities combined with a relatively small history table. Our technique reduces the number of extra row activations compared to static probabilistic techniques and it demands less storage than Tabled Counters techniques. Compared to state of the art, our technique offers a good compromise that has 9× - 27× reduced storage requirement than Tabled Counters and 6× - 12× fewer activations than probabilistic techniques.