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It's now possible to get purgeable memory by using mmap(MAP_PURGEABLE). Purgeable memory has a "volatile" flag that can be set using madvise(): - madvise(..., MADV_SET_VOLATILE) - madvise(..., MADV_SET_NONVOLATILE) When in the "volatile" state, the kernel may take away the underlying physical memory pages at any time, without notifying the owner. This gives you a guilt discount when caching very large things. :^) Setting a purgeable region to non-volatile will return whether or not the memory has been taken away by the kernel while being volatile. Basically, if madvise(..., MADV_SET_NONVOLATILE) returns 1, that means the memory was purged while volatile, and whatever was in that piece of memory needs to be reconstructed before use.
41 lines
910 B
C++
41 lines
910 B
C++
#include <Kernel/VM/PurgeableVMObject.h>
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#include <Kernel/VM/PhysicalPage.h>
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NonnullRefPtr<PurgeableVMObject> PurgeableVMObject::create_with_size(size_t size)
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{
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return adopt(*new PurgeableVMObject(size));
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}
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PurgeableVMObject::PurgeableVMObject(size_t size)
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: AnonymousVMObject(size)
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{
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}
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PurgeableVMObject::PurgeableVMObject(const PurgeableVMObject& other)
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: AnonymousVMObject(other)
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{
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}
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PurgeableVMObject::~PurgeableVMObject()
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{
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}
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NonnullRefPtr<VMObject> PurgeableVMObject::clone()
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{
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return adopt(*new PurgeableVMObject(*this));
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}
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int PurgeableVMObject::purge()
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{
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LOCKER(m_paging_lock);
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if (!m_volatile)
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return 0;
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int purged_page_count = 0;
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for (size_t i = 0; i < m_physical_pages.size(); ++i) {
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if (m_physical_pages[i])
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++purged_page_count;
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m_physical_pages[i] = nullptr;
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}
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m_was_purged = true;
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return purged_page_count;
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}
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