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PATH: Page Access Tracking to Improve Memory Management

Reza Azimi, Livio Soares, Michael Stumm, Angela Demke Brown and Tom Walsh

The 2007 International Symposium on Memory Management (ISMM 2007)
Montreal, Canada, 21-22 October, 2007


Traditionally, operating systems use a coarse approximation of memory accesses to implement memory management algorithms by monitoring page faults or scanning page table entries. With finer-grained memory access information, however, the operating system can manage memory much more effectively. Previous work has proposed the use of a software mechanism based on virtual page protection and soft faults to track page accesses at finer granularity. In this paper, we show that while this approach is effective for some applications, for many others it results in an unacceptably high overhead.

We propose simple Page Access Tracking Hardware (PATH) to provide more accurate page access information to the operating system. The suggested hardware support is generic and can be used by various memory management algorithms. In this paper, we show how the information generated by PATH can be used to implement (i) adaptive page replacement policies, (ii) smart process memory allocation to improve performance or to provide isolation and better process prioritization, and (iii) effectively prefetch virtual memory pages when applications have non-trivial memory access patterns. Our simulation results show that these algorithms can dramatically improve performance (up to 500%) with PATH-provided information, especially when the system is under memory pressure. Using an emulation technique, we show the software overhead of processing PATH information is is less than 6% across the applications we examined (less than 3% in all but two applications), which is at least an order of magnitude less than the overhead of existing software approaches.

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