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This patch adds a globally shared zero-filled PhysicalPage that will be mapped into every slot of every zero-filled AnonymousVMObject until that page is written to, achieving CoW-like zero-filled pages. Initial testing show that this doesn't actually achieve any sharing yet but it seems like a good design regardless, since it may reduce the number of page faults taken by programs. If you look at the refcount of MM.shared_zero_page() it will have quite a high refcount, but that's just because everything maps it everywhere. If you want to see the "real" refcount, you can build with the MAP_SHARED_ZERO_PAGE_LAZILY flag, and we'll defer mapping of the shared zero page until the first NP read fault. I've left this behavior behind a flag for future testing of this code. |
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| .. | ||
| AnonymousVMObject.cpp | ||
| AnonymousVMObject.h | ||
| InodeVMObject.cpp | ||
| InodeVMObject.h | ||
| MemoryManager.cpp | ||
| MemoryManager.h | ||
| PageDirectory.cpp | ||
| PageDirectory.h | ||
| PhysicalPage.cpp | ||
| PhysicalPage.h | ||
| PhysicalRegion.cpp | ||
| PhysicalRegion.h | ||
| PurgeableVMObject.cpp | ||
| PurgeableVMObject.h | ||
| RangeAllocator.cpp | ||
| RangeAllocator.h | ||
| Region.cpp | ||
| Region.h | ||
| VMObject.cpp | ||
| VMObject.h | ||