js/src/gc/Memory.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef gc_Memory_h
   8 #define gc_Memory_h
   9
  10 #include <stddef.h>
  11
  12 namespace js {
  13 namespace gc {
  14
  15 // Sanity check that our compiled configuration matches the currently
  16 // running instance and initialize any runtime data needed for allocation.
  17 void InitMemorySubsystem();
  18
  19 // The page size as reported by the operating system.
  20 size_t SystemPageSize();
  21
  22 // The number of bits that may be set in a valid address, as
  23 // reported by the operating system or measured at startup.
  24 size_t SystemAddressBits();
  25
  26 // The number of bytes of virtual memory that may be allocated or mapped, as
  27 // reported by the operating system on certain platforms. If no limit was able
  28 // to be determined, then it will be size_t(-1).
  29 size_t VirtualMemoryLimit();
  30
  31 // The scattershot allocator is used on platforms that have a large address
  32 // range. On these platforms we allocate at random addresses.
  33 bool UsingScattershotAllocator();
  34
  35 // Allocate or deallocate pages from the system with the given alignment.
  36 // Pages will be read/write-able.
  37 void* MapAlignedPages(size_t length, size_t alignment);
  38 void UnmapPages(void* region, size_t length);
  39
  40 // We can only decommit unused pages if the page size is less than or equal to
  41 // the hardcoded Arena size for the running process.
  42 bool DecommitEnabled();
  43
  44 // Tell the OS that the given pages are not in use, so they should not be
  45 // written to a paging file. This may be a no-op on some platforms.
  46 bool MarkPagesUnusedSoft(void* region, size_t length);
  47
  48 // Tell the OS that the given pages are not in use and it can decommit them
  49 // immediately. This may defer to MarkPagesUnusedSoft and must be paired with
  50 // MarkPagesInUse to use the pages again.
  51 bool MarkPagesUnusedHard(void* region, size_t length);
  52
  53 // Undo |MarkPagesUnusedSoft|: tell the OS that the given pages are of interest
  54 // and should be paged in and out normally. This may be a no-op on some
  55 // platforms.  May make pages read/write-able.
  56 void MarkPagesInUseSoft(void* region, size_t length);
  57
  58 // Undo |MarkPagesUnusedHard|: tell the OS that the given pages are of interest
  59 // and should be paged in and out normally. This may be a no-op on some
  60 // platforms. Callers must check the result, false could mean that the pages
  61 // are not available.  May make pages read/write.
  62 [[nodiscard]] bool MarkPagesInUseHard(void* region, size_t length);
  63
  64 // Returns #(hard faults) + #(soft faults)
  65 size_t GetPageFaultCount();
  66
  67 // Allocate memory mapped content.
  68 // The offset must be aligned according to alignment requirement.
  69 void* AllocateMappedContent(int fd, size_t offset, size_t length,
  70                             size_t alignment);
  71
  72 // Deallocate memory mapped content.
  73 void DeallocateMappedContent(void* region, size_t length);
  74
  75 void* TestMapAlignedPagesLastDitch(size_t length, size_t alignment);
  76
  77 void ProtectPages(void* region, size_t length);
  78 void MakePagesReadOnly(void* region, size_t length);
  79 void UnprotectPages(void* region, size_t length);
  80
  81 }  // namespace gc
  82 }  // namespace js
  83
  84 #endif /* gc_Memory_h */