< prev index next > src/hotspot/share/memory/memoryReserver.cpp
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// Create protection page at the beginning of the space.
static ReservedSpace establish_noaccess_prefix(const ReservedSpace& reserved, size_t noaccess_prefix) {
assert(reserved.alignment() >= os::vm_page_size(), "must be at least page size big");
assert(reserved.is_reserved(), "should only be called on a reserved memory area");
! if (reserved.end() > (char *)OopEncodingHeapMax) {
if (true
WIN64_ONLY(&& !UseLargePages)
AIX_ONLY(&& (os::Aix::supports_64K_mmap_pages() || os::vm_page_size() == 4*K))) {
// Protect memory at the base of the allocated region.
if (!os::protect_memory(reserved.base(), noaccess_prefix, os::MEM_PROT_NONE, reserved.special())) {
// Create protection page at the beginning of the space.
static ReservedSpace establish_noaccess_prefix(const ReservedSpace& reserved, size_t noaccess_prefix) {
assert(reserved.alignment() >= os::vm_page_size(), "must be at least page size big");
assert(reserved.is_reserved(), "should only be called on a reserved memory area");
! if (reserved.end() > (char *)OopEncodingHeapMax || UseCompatibleCompressedOops) {
+ assert((reserved.base() != nullptr), "sanity");
if (true
WIN64_ONLY(&& !UseLargePages)
AIX_ONLY(&& (os::Aix::supports_64K_mmap_pages() || os::vm_page_size() == 4*K))) {
// Protect memory at the base of the allocated region.
if (!os::protect_memory(reserved.base(), noaccess_prefix, os::MEM_PROT_NONE, reserved.special())) {
NOT_AIX(os::vm_allocation_granularity());
const size_t attach_point_alignment = lcm(alignment, os_attach_point_alignment);
char* aligned_heap_base_min_address = align_up((char*)HeapBaseMinAddress, alignment);
! size_t noaccess_prefix = ((aligned_heap_base_min_address + size) > (char*)OopEncodingHeapMax) ?
! noaccess_prefix_size : 0;
ReservedSpace reserved{};
// Attempt to alloc at user-given address.
! if (!FLAG_IS_DEFAULT(HeapBaseMinAddress)) {
reserved = try_reserve_memory(size + noaccess_prefix, alignment, page_size, aligned_heap_base_min_address);
if (reserved.base() != aligned_heap_base_min_address) { // Enforce this exact address.
release(reserved);
reserved = {};
}
NOT_AIX(os::vm_allocation_granularity());
const size_t attach_point_alignment = lcm(alignment, os_attach_point_alignment);
char* aligned_heap_base_min_address = align_up((char*)HeapBaseMinAddress, alignment);
! char* heap_end_address = aligned_heap_base_min_address + size;
!
+ bool unscaled = false;
+ bool zerobased = false;
+ if (!UseCompatibleCompressedOops) { // heap base is not enforced
+ unscaled = (heap_end_address <= (char*)UnscaledOopHeapMax);
+ zerobased = (heap_end_address <= (char*)OopEncodingHeapMax);
+ }
+ size_t noaccess_prefix = !zerobased ? noaccess_prefix_size : 0;
ReservedSpace reserved{};
// Attempt to alloc at user-given address.
! if (!FLAG_IS_DEFAULT(HeapBaseMinAddress) || UseCompatibleCompressedOops) {
reserved = try_reserve_memory(size + noaccess_prefix, alignment, page_size, aligned_heap_base_min_address);
if (reserved.base() != aligned_heap_base_min_address) { // Enforce this exact address.
release(reserved);
reserved = {};
}
// address. try_reserve_heap() always returns this allocated memory, as only here
// the criteria for a good heap are checked.
// Attempt to allocate so that we can run without base and scale (32-Bit unscaled compressed oops).
// Give it several tries from top of range to bottom.
! if (aligned_heap_base_min_address + size <= (char *)UnscaledOopHeapMax) {
// Calc address range within we try to attach (range of possible start addresses).
char* const highest_start = align_down((char *)UnscaledOopHeapMax - size, attach_point_alignment);
char* const lowest_start = align_up(aligned_heap_base_min_address, attach_point_alignment);
reserved = try_reserve_range(highest_start, lowest_start, attach_point_alignment,
// address. try_reserve_heap() always returns this allocated memory, as only here
// the criteria for a good heap are checked.
// Attempt to allocate so that we can run without base and scale (32-Bit unscaled compressed oops).
// Give it several tries from top of range to bottom.
! if (unscaled) {
// Calc address range within we try to attach (range of possible start addresses).
char* const highest_start = align_down((char *)UnscaledOopHeapMax - size, attach_point_alignment);
char* const lowest_start = align_up(aligned_heap_base_min_address, attach_point_alignment);
reserved = try_reserve_range(highest_start, lowest_start, attach_point_alignment,
// zerobased: Attempt to allocate in the lower 32G.
char *zerobased_max = (char *)OopEncodingHeapMax;
// Give it several tries from top of range to bottom.
! if (aligned_heap_base_min_address + size <= zerobased_max && // Zerobased theoretical possible.
! ((!reserved.is_reserved()) || // No previous try succeeded.
! (reserved.end() > zerobased_max))) { // Unscaled delivered an arbitrary address.
// Release previous reservation
release(reserved);
// Calc address range within we try to attach (range of possible start addresses).
// zerobased: Attempt to allocate in the lower 32G.
char *zerobased_max = (char *)OopEncodingHeapMax;
// Give it several tries from top of range to bottom.
! if (zerobased && // Zerobased theoretical possible.
! ((!reserved.is_reserved()) || // No previous try succeeded.
! (reserved.end() > zerobased_max))) { // Unscaled delivered an arbitrary address.
// Release previous reservation
release(reserved);
// Calc address range within we try to attach (range of possible start addresses).
assert(reserved.size() == size, "Prefix should be gone");
return ReservedHeapSpace(reserved, noaccess_prefix);
}
// We reserved heap memory without a noaccess prefix.
+ assert(!UseCompatibleCompressedOops, "noaccess prefix is missing");
return ReservedHeapSpace(reserved, 0 /* noaccess_prefix */);
}
// Failed
return {};
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