1. The Scalable Commutativity Rule: Designing Scalable Software for Multicore Processors
A. T. Clements, M. F. Kaashoek, N.Zeldovich, R. T. Morris, and E. Kohler†
MIT CSAIL and †Harvard

2. Paper Highlights
Presents an general efficient mechanism to manage pages of different sizes in a VM system
Superpages
Objective is to address the limitations of extant translation lookaside buffers (TLB).

3. MESI Coherency protocol (I)
Write-through cache and memory consistency protocol
Name refers to four possible states for cache lines
Modified (locked and dirty)
Exclusive (locked and clean)
Shared (unlocked and clean)
Invalid
Common-sense transitions between states

4. Snooping
Any cache that hold a line in the modified state must intercept and service all attempted read accesses to that line from other caches
Any cache that holds a line in the shared state must act on invalidate or request-for-ownership broadcasts from other caches
A cache that holds a line in the Exclusive state must snoop all read requests to that line from all other caches, and move the line to shared state if needed

5. Optimizations Store buffers allow caches to write into invalid lines
Invalidation queues contain invalidation requests that have not yet been acted upon
Weaken consistency and require barriers
Store barriers flush the store buffers
Read barrier flush the invalidation queue