void G1PageBasedVirtualSpace::initialize_with_page_size(ReservedSpace rs, size_t used_size, size_t page_size) {
guarantee(rs.is_reserved(), "Given reserved space must have been reserved already.");
vmassert(_low_boundary == NULL, "VirtualSpace already initialized");
vmassert(page_size > 0, "Page size must be non-zero.");
guarantee(is_ptr_aligned(rs.base(), page_size),
"Reserved space base " PTR_FORMAT " is not aligned to requested page size " SIZE_FORMAT, p2i(rs.base()), page_size);
guarantee(is_size_aligned(used_size, os::vm_page_size()),
"Given used reserved space size needs to be OS page size aligned (%d bytes) but is " SIZE_FORMAT, os::vm_page_size(), used_size);
guarantee(used_size <= rs.size(),
"Used size of reserved space " SIZE_FORMAT " bytes is smaller than reservation at " SIZE_FORMAT " bytes", used_size, rs.size());
guarantee(is_size_aligned(rs.size(), page_size),
"Expected that the virtual space is size aligned, but " SIZE_FORMAT " is not aligned to page size " SIZE_FORMAT, rs.size(), page_size);
_low_boundary = rs.base();
_high_boundary = _low_boundary + used_size;
_special = rs.special();
_executable = rs.executable();
_page_size = page_size;
vmassert(_committed.size() == 0, "virtual space initialized more than once");
BitMap::idx_t size_in_pages = rs.size() / page_size;
_committed.initialize(size_in_pages);
if (_special) {
_dirty.initialize(size_in_pages);
}
_tail_size = used_size % _page_size;
}
bool VirtualSpace::initialize_with_granularity(ReservedSpace rs, size_t committed_size, size_t max_commit_granularity) {
if(!rs.is_reserved()) return false; // allocation failed.
assert(_low_boundary == NULL, "VirtualSpace already initialized");
assert(max_commit_granularity > 0, "Granularity must be non-zero.");
_low_boundary = rs.base();
_high_boundary = low_boundary() + rs.size();
_low = low_boundary();
_high = low();
_special = rs.special();
_executable = rs.executable();
// When a VirtualSpace begins life at a large size, make all future expansion
// and shrinking occur aligned to a granularity of large pages. This avoids
// fragmentation of physical addresses that inhibits the use of large pages
// by the OS virtual memory system. Empirically, we see that with a 4MB
// page size, the only spaces that get handled this way are codecache and
// the heap itself, both of which provide a substantial performance
// boost in many benchmarks when covered by large pages.
//
// No attempt is made to force large page alignment at the very top and
// bottom of the space if they are not aligned so already.
_lower_alignment = os::vm_page_size();
_middle_alignment = max_commit_granularity;
_upper_alignment = os::vm_page_size();
// End of each region
_lower_high_boundary = (char*) round_to((intptr_t) low_boundary(), middle_alignment());
_middle_high_boundary = (char*) round_down((intptr_t) high_boundary(), middle_alignment());
_upper_high_boundary = high_boundary();
// High address of each region
_lower_high = low_boundary();
_middle_high = lower_high_boundary();
_upper_high = middle_high_boundary();
// commit to initial size
if (committed_size > 0) {
if (!expand_by(committed_size)) {
return false;
}
}
return true;
}
bool G1PageBasedVirtualSpace::initialize_with_granularity(ReservedSpace rs, size_t page_size) {
if (!rs.is_reserved()) {
return false; // Allocation failed.
}
assert(_low_boundary == NULL, "VirtualSpace already initialized");
assert(page_size > 0, "Granularity must be non-zero.");
_low_boundary = rs.base();
_high_boundary = _low_boundary + rs.size();
_special = rs.special();
_executable = rs.executable();
_page_size = page_size;
assert(_committed.size() == 0, "virtual space initialized more than once");
uintx size_in_bits = rs.size() / page_size;
_committed.resize(size_in_bits, /* in_resource_area */ false);
return true;
}