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Kernel: Make purgeable memory a VMObject level concept (again)

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This patch changes the semantics of purgeable memory.

- AnonymousVMObject now has a "purgeable" flag. It can only be set when
  constructing the object. (Previously, all anonymous memory was
  effectively purgeable.)

- AnonymousVMObject now has a "volatile" flag. It covers the entire
  range of physical pages. (Previously, we tracked ranges of volatile
  pages, effectively making it a page-level concept.)

- Non-volatile objects maintain a physical page reservation via the
  committed pages mechanism, to ensure full coverage for page faults.

- When an object is made volatile, it relinquishes any unused committed
  pages immediately. If later made non-volatile again, we then attempt
  to make a new committed pages reservation. If this fails, we return
  ENOMEM to userspace.

mmap() now creates purgeable objects if passed the MAP_PURGEABLE option
together with MAP_ANONYMOUS. anon_create() memory is always purgeable.
This commit is contained in:
Andreas Kling 2021-07-25 01:46:44 +02:00
parent 6bb53d6a80
commit 2d1a651e0a
17 changed files with 189 additions and 1004 deletions
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17
Kernel/VM/Region.h
View file

@ -17,7 +17,6 @@
#include <Kernel/Sections.h>
#include <Kernel/UnixTypes.h>
#include <Kernel/VM/PageFaultResponse.h>
#include <Kernel/VM/PurgeablePageRanges.h>
#include <Kernel/VM/RangeAllocator.h>
namespace Kernel {
@ -28,8 +27,7 @@ enum class ShouldFlushTLB {
};
class Region final
: public Weakable<Region>
, public PurgeablePageRanges {
: public Weakable<Region> {
friend class MemoryManager;
MAKE_SLAB_ALLOCATED(Region)
@ -201,15 +199,11 @@ public:
void remap();
bool remap_vmobject_page_range(size_t page_index, size_t page_count);
bool is_volatile(VirtualAddress vaddr, size_t size) const;
enum class SetVolatileError {
Success = 0,
NotPurgeable,
OutOfMemory
};
SetVolatileError set_volatile(VirtualAddress vaddr, size_t size, bool is_volatile, bool& was_purged);
RefPtr<Process> get_owner();
@ -219,7 +213,8 @@ public:
private:
Region(Range const&, NonnullRefPtr<VMObject>, size_t offset_in_vmobject, OwnPtr<KString>, Region::Access access, Cacheable, bool shared);
bool do_remap_vmobject_page_range(size_t page_index, size_t page_count);
bool remap_vmobject_page(size_t page_index, bool with_flush = true);
bool do_remap_vmobject_page(size_t page_index, bool with_flush = true);
void set_access_bit(Access access, bool b)
{
@ -229,18 +224,12 @@ private:
m_access &= ~access;
}
bool do_remap_vmobject_page(size_t index, bool with_flush = true);
bool remap_vmobject_page(size_t index, bool with_flush = true);
PageFaultResponse handle_cow_fault(size_t page_index);
PageFaultResponse handle_inode_fault(size_t page_index);
PageFaultResponse handle_zero_fault(size_t page_index);
bool map_individual_page_impl(size_t page_index);
void register_purgeable_page_ranges();
void unregister_purgeable_page_ranges();
RefPtr<PageDirectory> m_page_directory;
Range m_range;
size_t m_offset_in_vmobject { 0 };