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Kernel: Implement lazy committed page allocation

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

View file

@ -48,12 +48,12 @@ private:
};
public:
SharedBuffer(int id, int size)
SharedBuffer(int id, NonnullRefPtr<PurgeableVMObject>&& vmobject)
: m_shbuf_id(id)
, m_vmobject(PurgeableVMObject::create_with_size(size))
, m_vmobject(move(vmobject))
{
#ifdef SHARED_BUFFER_DEBUG
dbg() << "Created shared buffer " << m_shbuf_id << " of size " << size;
dbg() << "Created shared buffer " << m_shbuf_id << " of size " << m_vmobject->size();
#endif
}