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After a fork(), page faults on anonymous mmaps can cause a redundant page fault to occur. This happens because VMObjects for anonymous mmaps are initially filled with references to the lazy_committed_page or shared_zero_page. If there is a fork, VMObject::try_clone() is called and all pages of the VMObject are marked as cow (via the m_cow_map). Page faults on a zero/lazy page are handled by handle_zero_fault(). handle_zero_fault() does not update m_cow_map, so if the page was marked cow before the fault, it will still be marked cow after the fault. This causes a second (redundant) page fault when the CPU retries the write. This commit removes the redundant page fault by not marking zero/lazy pages as cow in m_cow_map. |
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| .. | ||
| API | ||
| Arch | ||
| Boot | ||
| Bus | ||
| Devices | ||
| FileSystem | ||
| Firmware/ACPI | ||
| Heap | ||
| Interrupts | ||
| Library | ||
| Locking | ||
| Memory | ||
| Net | ||
| Prekernel | ||
| Security | ||
| Syscalls | ||
| Tasks | ||
| Time | ||
| CMakeLists.txt | ||
| Debug.h.in | ||
| embedmap.sh | ||
| Forward.h | ||
| generate-version-file.sh | ||
| kprintf.cpp | ||
| kstdio.h | ||
| KSyms.cpp | ||
| KSyms.h | ||
| mkmap.sh | ||
| SanCov.cpp | ||
| Sections.h | ||
| UnixTypes.h | ||