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Kernel: Implement lazy committed page allocation

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By designating a committed page pool we can guarantee to have physical
pages available for lazy allocation in mappings. However, when forking
we will overcommit. The assumption is that worst-case it's better for
the fork to die due to insufficient physical memory on COW access than
the parent that created the region. If a fork wants to ensure that all
memory is available (trigger a commit) then it can use madvise.

This also means that fork now can gracefully fail if we don't have
enough physical pages available.
This commit is contained in:
Tom 2020-09-04 21:12:25 -06:00 • committed by Andreas Kling
parent e21cc4cff6
commit b2a52f6208
20 changed files with 329 additions and 67 deletions
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4
Kernel/VM/Region.h
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@ -105,7 +105,7 @@ public:
PageFaultResponse handle_fault(const PageFault&);
NonnullOwnPtr<Region> clone();
OwnPtr<Region> clone();
bool contains(VirtualAddress vaddr) const
{
@ -194,7 +194,7 @@ public:
void set_inherit_mode(InheritMode inherit_mode) { m_inherit_mode = inherit_mode; }
bool remap_page_range(size_t page_index, size_t page_count, bool do_commit);
bool remap_page_range(size_t page_index, size_t page_count);
bool is_volatile(VirtualAddress vaddr, size_t size) const;
enum class SetVolatileError {