8253650: Cleanup: remove alignment_hint parameter from os::reserve_memory

Reviewed-by: stefank, tschatzl

Author: tstuefe

src/hotspot/os/aix/os_aix.cpp

@@ -1925,21 +1925,10 @@ static void vmembk_print_on(outputStream* os) {
 // If <requested_addr> is not NULL, function will attempt to attach the memory at the given
 // address. Failing that, it will attach the memory anywhere.
 // If <requested_addr> is NULL, function will attach the memory anywhere.
-//
-// <alignment_hint> is being ignored by this function. It is very probable however that the
-// alignment requirements are met anyway, because shmat() attaches at 256M boundaries.
-// Should this be not enogh, we can put more work into it.
-static char* reserve_shmated_memory (
-  size_t bytes,
-  char* requested_addr,
-  size_t alignment_hint) {
+static char* reserve_shmated_memory (size_t bytes, char* requested_addr) {
 
   trcVerbose("reserve_shmated_memory " UINTX_FORMAT " bytes, wishaddress "
-    PTR_FORMAT ", alignment_hint " UINTX_FORMAT "...",
-    bytes, p2i(requested_addr), alignment_hint);
-
-  // Either give me wish address or wish alignment but not both.
-  assert0(!(requested_addr != NULL && alignment_hint != 0));
+    PTR_FORMAT "...", bytes, p2i(requested_addr));
 
   // We must prevent anyone from attaching too close to the
   // BRK because that may cause malloc OOM.
@@ -2061,15 +2050,10 @@ static bool uncommit_shmated_memory(char* addr, size_t size) {
 // Reserve memory via mmap.
 // If <requested_addr> is given, an attempt is made to attach at the given address.
 // Failing that, memory is allocated at any address.
-// If <alignment_hint> is given and <requested_addr> is NULL, an attempt is made to
-// allocate at an address aligned with the given alignment. Failing that, memory
-// is aligned anywhere.
-static char* reserve_mmaped_memory(size_t bytes, char* requested_addr, size_t alignment_hint) {
-  trcVerbose("reserve_mmaped_memory " UINTX_FORMAT " bytes, wishaddress " PTR_FORMAT ", "
-    "alignment_hint " UINTX_FORMAT "...",
-    bytes, p2i(requested_addr), alignment_hint);
-
-  // If a wish address is given, but not aligned to 4K page boundary, mmap will fail.
+static char* reserve_mmaped_memory(size_t bytes, char* requested_addr) {
+  trcVerbose("reserve_mmaped_memory " UINTX_FORMAT " bytes, wishaddress " PTR_FORMAT "...",
+    bytes, p2i(requested_addr));
+
   if (requested_addr && !is_aligned_to(requested_addr, os::vm_page_size()) != 0) {
     trcVerbose("Wish address " PTR_FORMAT " not aligned to page boundary.", p2i(requested_addr));
     return NULL;
@@ -2084,26 +2068,21 @@ static char* reserve_mmaped_memory(size_t bytes, char* requested_addr, size_t al
     requested_addr = NULL;
   }
 
-  // Specify one or the other but not both.
-  assert0(!(requested_addr != NULL && alignment_hint > 0));
-
-  // In 64K mode, we claim the global page size (os::vm_page_size())
-  // is 64K. This is one of the few points where that illusion may
-  // break, because mmap() will always return memory aligned to 4K. So
-  // we must ensure we only ever return memory aligned to 64k.
-  if (alignment_hint) {
-    alignment_hint = lcm(alignment_hint, os::vm_page_size());
-  } else {
-    alignment_hint = os::vm_page_size();
-  }
+  // In 64K mode, we lie and claim the global page size (os::vm_page_size()) is 64K
+  //  (complicated story). This mostly works just fine since 64K is a multiple of the
+  //  actual 4K lowest page size. Only at a few seams light shines thru, e.g. when
+  //  calling mmap. mmap will return memory aligned to the lowest pages size - 4K -
+  //  so we must make sure - transparently - that the caller only ever sees 64K
+  //  aligned mapping start addresses.
+  const size_t alignment = os::vm_page_size();
 
   // Size shall always be a multiple of os::vm_page_size (esp. in 64K mode).
   const size_t size = align_up(bytes, os::vm_page_size());
 
   // alignment: Allocate memory large enough to include an aligned range of the right size and
   // cut off the leading and trailing waste pages.
-  assert0(alignment_hint != 0 && is_aligned_to(alignment_hint, os::vm_page_size())); // see above
-  const size_t extra_size = size + alignment_hint;
+  assert0(alignment != 0 && is_aligned_to(alignment, os::vm_page_size())); // see above
+  const size_t extra_size = size + alignment;
 
   // Note: MAP_SHARED (instead of MAP_PRIVATE) needed to be able to
   // later use msync(MS_INVALIDATE) (see os::uncommit_memory).
@@ -2131,7 +2110,7 @@ static char* reserve_mmaped_memory(size_t bytes, char* requested_addr, size_t al
   }
 
   // Handle alignment.
-  char* const addr_aligned = align_up(addr, alignment_hint);
+  char* const addr_aligned = align_up(addr, alignment);
   const size_t waste_pre = addr_aligned - addr;
   char* const addr_aligned_end = addr_aligned + size;
   const size_t waste_post = extra_size - waste_pre - size;
@@ -2347,21 +2326,19 @@ char *os::scan_pages(char *start, char* end, page_info* page_expected, page_info
 }
 
 // Reserves and attaches a shared memory segment.
-char* os::pd_reserve_memory(size_t bytes, size_t alignment_hint) {
+char* os::pd_reserve_memory(size_t bytes) {
   // Always round to os::vm_page_size(), which may be larger than 4K.
   bytes = align_up(bytes, os::vm_page_size());
-  const size_t alignment_hint0 =
-    alignment_hint ? align_up(alignment_hint, os::vm_page_size()) : 0;
 
   // In 4K mode always use mmap.
   // In 64K mode allocate small sizes with mmap, large ones with 64K shmatted.
   if (os::vm_page_size() == 4*K) {
-    return reserve_mmaped_memory(bytes, NULL /* requested_addr */, alignment_hint);
+    return reserve_mmaped_memory(bytes, NULL /* requested_addr */);
   } else {
     if (bytes >= Use64KPagesThreshold) {
-      return reserve_shmated_memory(bytes, NULL /* requested_addr */, alignment_hint);
+      return reserve_shmated_memory(bytes, NULL /* requested_addr */);
     } else {
-      return reserve_mmaped_memory(bytes, NULL /* requested_addr */, alignment_hint);
+      return reserve_mmaped_memory(bytes, NULL /* requested_addr */);
     }
   }
 }
@@ -2538,7 +2515,7 @@ char* os::pd_attempt_reserve_memory_at(char* requested_addr, size_t bytes, int f
 
   // Always round to os::vm_page_size(), which may be larger than 4K.
   bytes = align_up(bytes, os::vm_page_size());
-  result = reserve_mmaped_memory(bytes, requested_addr, 0);
+  result = reserve_mmaped_memory(bytes, requested_addr);
 
   if (result != NULL) {
     if (replace_existing_mapping_with_file_mapping(result, bytes, file_desc) == NULL) {
@@ -2559,12 +2536,12 @@ char* os::pd_attempt_reserve_memory_at(char* requested_addr, size_t bytes) {
   // In 4K mode always use mmap.
   // In 64K mode allocate small sizes with mmap, large ones with 64K shmatted.
   if (os::vm_page_size() == 4*K) {
-    return reserve_mmaped_memory(bytes, requested_addr, 0);
+    return reserve_mmaped_memory(bytes, requested_addr);
   } else {
     if (bytes >= Use64KPagesThreshold) {
-      return reserve_shmated_memory(bytes, requested_addr, 0);
+      return reserve_shmated_memory(bytes, requested_addr);
     } else {
-      return reserve_mmaped_memory(bytes, requested_addr, 0);
+      return reserve_mmaped_memory(bytes, requested_addr);
     }
   }
 

src/hotspot/os/bsd/os_bsd.cpp

@@ -2030,8 +2030,7 @@ static int anon_munmap(char * addr, size_t size) {
   return ::munmap(addr, size) == 0;
 }
 
-char* os::pd_reserve_memory(size_t bytes, size_t alignment_hint) {
-  // Ignores alignment hint
+char* os::pd_reserve_memory(size_t bytes) {
   return anon_mmap(NULL /* addr */, bytes);
 }
 

src/hotspot/os/linux/os_linux.cpp

@@ -3694,8 +3694,7 @@ static int anon_munmap(char * addr, size_t size) {
   return ::munmap(addr, size) == 0;
 }
 
-char* os::pd_reserve_memory(size_t bytes, size_t alignment_hint) {
-  // Ignores alignment hint
+char* os::pd_reserve_memory(size_t bytes) {
   return anon_mmap(NULL, bytes);
 }
 

src/hotspot/os/posix/os_posix.cpp

@@ -316,17 +316,18 @@ char* os::reserve_memory_aligned(size_t size, size_t alignment, int file_desc) {
 
   char* extra_base;
   if (file_desc != -1) {
-    // For file mapping, we do not call os:reserve_memory(extra_size, NULL, alignment, file_desc) because
-    // we need to deal with shrinking of the file space later when we release extra memory after alignment.
-    // We also cannot called os:reserve_memory() with file_desc set to -1 because on aix we might get SHM memory.
-    // So here to call a helper function while reserve memory for us. After we have a aligned base,
-    // we will replace anonymous mapping with file mapping.
+    // For file mapping, we do not call os:reserve_memory_with_fd since:
+    // - we later chop away parts of the mapping using os::release_memory and that could fail if the
+    //   original mmap call had been tied to an fd.
+    // - The memory API os::reserve_memory uses is an implementation detail. It may (and usually is)
+    //   mmap but it also may System V shared memory which cannot be uncommitted as a whole, so
+    //   chopping off and unmapping excess bits back and front (see below) would not work.
     extra_base = reserve_mmapped_memory(extra_size, NULL);
     if (extra_base != NULL) {
       MemTracker::record_virtual_memory_reserve((address)extra_base, extra_size, CALLER_PC);
     }
   } else {
-    extra_base = os::reserve_memory(extra_size, alignment);
+    extra_base = os::reserve_memory(extra_size);
   }
 
   if (extra_base == NULL) {

src/hotspot/os/windows/os_windows.cpp

@@ -3086,7 +3086,7 @@ char* os::reserve_memory_aligned(size_t size, size_t alignment, int file_desc) {
   char* aligned_base = NULL;
 
   do {
-    char* extra_base = os::reserve_memory_with_fd(extra_size, alignment, file_desc);
+    char* extra_base = os::reserve_memory_with_fd(extra_size, file_desc);
     if (extra_base == NULL) {
       return NULL;
     }
@@ -3106,8 +3106,7 @@ char* os::reserve_memory_aligned(size_t size, size_t alignment, int file_desc) {
   return aligned_base;
 }
 
-char* os::pd_reserve_memory(size_t bytes, size_t alignment_hint) {
-  // Ignores alignment hint
+char* os::pd_reserve_memory(size_t bytes) {
   return pd_attempt_reserve_memory_at(NULL /* addr */, bytes);
 }
 

src/hotspot/share/gc/z/zMarkStackAllocator.cpp

@@ -42,8 +42,7 @@ ZMarkStackSpace::ZMarkStackSpace() :
 
   // Reserve address space
   const size_t size = ZMarkStackSpaceLimit;
-  const size_t alignment = (size_t)os::vm_allocation_granularity();
-  const uintptr_t addr = (uintptr_t)os::reserve_memory(size, alignment, mtGC);
+  const uintptr_t addr = (uintptr_t)os::reserve_memory(size, mtGC);
   if (addr == 0) {
     log_error_pd(gc, marking)("Failed to reserve address space for mark stacks");
     return;

src/hotspot/share/memory/allocation.inline.hpp

@@ -55,9 +55,8 @@ size_t MmapArrayAllocator<E>::size_for(size_t length) {
 template <class E>
 E* MmapArrayAllocator<E>::allocate_or_null(size_t length, MEMFLAGS flags) {
   size_t size = size_for(length);
-  int alignment = os::vm_allocation_granularity();
 
-  char* addr = os::reserve_memory(size, alignment, flags);
+  char* addr = os::reserve_memory(size, flags);
   if (addr == NULL) {
     return NULL;
   }
@@ -73,9 +72,8 @@ E* MmapArrayAllocator<E>::allocate_or_null(size_t length, MEMFLAGS flags) {
 template <class E>
 E* MmapArrayAllocator<E>::allocate(size_t length, MEMFLAGS flags) {
   size_t size = size_for(length);
-  int alignment = os::vm_allocation_granularity();
 
-  char* addr = os::reserve_memory(size, alignment, flags);
+  char* addr = os::reserve_memory(size, flags);
   if (addr == NULL) {
     vm_exit_out_of_memory(size, OOM_MMAP_ERROR, "Allocator (reserve)");
   }

src/hotspot/share/memory/virtualspace.cpp

@@ -179,7 +179,7 @@ void ReservedSpace::initialize(size_t size, size_t alignment, bool large,
   }
 
   if (base == NULL) {
-    // Optimistically assume that the OSes returns an aligned base pointer.
+    // Optimistically assume that the OS returns an aligned base pointer.
     // When reserving a large address range, most OSes seem to align to at
     // least 64K.
 
@@ -194,7 +194,7 @@ void ReservedSpace::initialize(size_t size, size_t alignment, bool large,
         base = NULL;
       }
     } else {
-      base = os::reserve_memory_with_fd(size, alignment, _fd_for_heap);
+      base = os::reserve_memory_with_fd(size, _fd_for_heap);
     }
 
     if (base == NULL) return;
@@ -371,18 +371,14 @@ void ReservedHeapSpace::try_reserve_heap(size_t size,
       log_debug(gc, heap, coops)("Reserve regular memory without large pages");
     }
 
-    // Optimistically assume that the OSes returns an aligned base pointer.
-    // When reserving a large address range, most OSes seem to align to at
-    // least 64K.
-
-    // If the memory was requested at a particular address, use
-    // os::attempt_reserve_memory_at() to avoid over mapping something
-    // important.  If available space is not detected, return NULL.
-
     if (requested_address != 0) {
       base = os::attempt_reserve_memory_at(requested_address, size, _fd_for_heap);
     } else {
-      base = os::reserve_memory_with_fd(size, alignment, _fd_for_heap);
+      // Optimistically assume that the OSes returns an aligned base pointer.
+      // When reserving a large address range, most OSes seem to align to at
+      // least 64K.
+      // If the returned memory is not aligned we will release and retry.
+      base = os::reserve_memory_with_fd(size, _fd_for_heap);
     }
   }
   if (base == NULL) { return; }

src/hotspot/share/runtime/os.cpp

@@ -1652,8 +1652,8 @@ bool os::create_stack_guard_pages(char* addr, size_t bytes) {
   return os::pd_create_stack_guard_pages(addr, bytes);
 }
 
-char* os::reserve_memory(size_t bytes, size_t alignment_hint, MEMFLAGS flags) {
-  char* result = pd_reserve_memory(bytes, alignment_hint);
+char* os::reserve_memory(size_t bytes, MEMFLAGS flags) {
+  char* result = pd_reserve_memory(bytes);
   if (result != NULL) {
     MemTracker::record_virtual_memory_reserve(result, bytes, CALLER_PC);
     if (flags != mtOther) {
@@ -1664,7 +1664,7 @@ char* os::reserve_memory(size_t bytes, size_t alignment_hint, MEMFLAGS flags) {
   return result;
 }
 
-char* os::reserve_memory_with_fd(size_t bytes, size_t alignment_hint, int file_desc) {
+char* os::reserve_memory_with_fd(size_t bytes, int file_desc) {
   char* result;
 
   if (file_desc != -1) {
@@ -1675,7 +1675,7 @@ char* os::reserve_memory_with_fd(size_t bytes, size_t alignment_hint, int file_d
       MemTracker::record_virtual_memory_reserve_and_commit(result, bytes, CALLER_PC);
     }
   } else {
-    result = pd_reserve_memory(bytes, alignment_hint);
+    result = pd_reserve_memory(bytes);
     if (result != NULL) {
       MemTracker::record_virtual_memory_reserve(result, bytes, CALLER_PC);
     }

src/hotspot/share/runtime/os.hpp

@@ -113,7 +113,7 @@ class os: AllStatic {
     _page_sizes[1] = 0; // sentinel
   }
 
-  static char*  pd_reserve_memory(size_t bytes, size_t alignment_hint);
+  static char*  pd_reserve_memory(size_t bytes);
 
   static char*  pd_attempt_reserve_memory_at(char* addr, size_t bytes);
   static char*  pd_attempt_reserve_memory_at(char* addr, size_t bytes, int file_desc);
@@ -314,11 +314,11 @@ class os: AllStatic {
 
   // Reserves virtual memory.
   // alignment_hint - currently only used by AIX
-  static char*  reserve_memory(size_t bytes, size_t alignment_hint = 0, MEMFLAGS flags = mtOther);
+  static char*  reserve_memory(size_t bytes, MEMFLAGS flags = mtOther);
 
   // Reserves virtual memory.
   // if file_desc != -1, also attaches the memory to the file.
-  static char*  reserve_memory_with_fd(size_t bytes, size_t alignment_hint, int file_desc);
+  static char*  reserve_memory_with_fd(size_t bytes, int file_desc);
 
   // Reserves virtual memory that starts at an address that is aligned to 'alignment'.
   static char*  reserve_memory_aligned(size_t size, size_t alignment, int file_desc = -1);