2018-11-13 Jonathan Wakely <jwakely@redhat.com>
+ * src/c++17/memory_resource.cc (big_block): Improve comments.
+ (big_block::all_ones): Remove.
+ (big_block::big_block(size_t, size_t)): Use alloc_size.
+ (big_block::size()): Add comment, replace all_ones with equivalent
+ expression.
+ (big_block::align()): Shift value of correct type.
+ (big_block::alloc_size(size_t)): New function to round up size.
+ (__pool_resource::allocate(size_t, size_t)): Add comment.
+ (__pool_resource::deallocate(void*, size_t, size_t)): Likewise. Fix
+ incorrect assertion by using big_block::alloc_size(size_t).
+ * testsuite/20_util/unsynchronized_pool_resource/allocate.cc: Add
+ more tests for unpooled allocations.
+
* src/c++17/memory_resource.cc (bitset::full()): Handle edge case
for _M_next_word maximum value.
(bitset::get_first_unset(), bitset::set(size_type)): Use
// An oversized allocation that doesn't fit in a pool.
struct big_block
{
+ // Alignment must be a power-of-two so we only need to use enough bits
+ // to store the power, not the actual value:
static constexpr unsigned _S_alignbits
- = std::__log2p1((unsigned)numeric_limits<size_t>::digits) - 1;
+ = std::__log2p1((unsigned)numeric_limits<size_t>::digits - 1);
+ // Use the remaining bits to store the size:
static constexpr unsigned _S_sizebits
= numeric_limits<size_t>::digits - _S_alignbits;
// The maximum value that can be stored in _S_size
- static constexpr size_t all_ones = (1ull << _S_sizebits) - 1u;
- // The minimum size of a big block
+ static constexpr size_t all_ones = size_t(-1) >> _S_alignbits;
+ // The minimum size of a big block (smaller sizes will be rounded up).
static constexpr size_t min = 1u << _S_alignbits;
big_block(size_t bytes, size_t alignment)
- : _M_size((bytes + min - 1u) >> _S_alignbits),
+ : _M_size(alloc_size(bytes) >> _S_alignbits),
_M_align_exp(std::__log2p1(alignment) - 1u)
- {
- if (__builtin_expect(std::__countl_one(bytes) == _S_sizebits, false))
- _M_size = all_ones;
- }
+ { }
void* pointer = nullptr;
size_t _M_size : numeric_limits<size_t>::digits - _S_alignbits;
size_t size() const noexcept
{
- if (__builtin_expect(_M_size == all_ones, false))
+ // If all bits are set in _M_size it means the maximum possible size:
+ if (__builtin_expect(_M_size == (size_t(-1) >> _S_alignbits), false))
return (size_t)-1;
else
return _M_size << _S_alignbits;
}
- size_t align() const noexcept { return 1ul << _M_align_exp; }
+ size_t align() const noexcept { return size_t(1) << _M_align_exp; }
+
+ // Calculate size to be allocated instead of requested number of bytes.
+ // The requested value will be rounded up to a multiple of big_block::min,
+ // so the low _S_alignbits bits are all zero and don't need to be stored.
+ static constexpr size_t alloc_size(size_t bytes) noexcept
+ {
+ const size_t s = bytes + min - 1u;
+ if (__builtin_expect(s < bytes, false))
+ return size_t(-1); // addition wrapped past zero, return max value
+ else
+ return s & ~(min - 1u);
+ }
friend bool operator<(void* p, const big_block& b) noexcept
{ return less<void*>{}(p, b.pointer); }
{
auto& b = _M_unpooled.emplace_back(bytes, alignment);
__try {
+ // N.B. need to allocate b.size(), which might be larger than bytes.
void* p = resource()->allocate(b.size(), alignment);
b.pointer = p;
if (_M_unpooled.size() > 1)
}
void
- __pool_resource::deallocate(void* p, size_t bytes [[maybe_unused]],
- size_t alignment [[maybe_unused]])
+ __pool_resource::deallocate(void* p, size_t bytes, size_t alignment)
{
const auto it
= std::lower_bound(_M_unpooled.begin(), _M_unpooled.end(), p);
if (it != _M_unpooled.end() && it->pointer == p) // [[likely]]
{
const auto b = *it;
- __glibcxx_assert(b.size() == bytes);
+ __glibcxx_assert(b.size() == b.alloc_size(bytes));
__glibcxx_assert(b.align() == alignment);
_M_unpooled.erase(it);
+ // N.B. need to deallocate b.size(), which might be larger than bytes.
resource()->deallocate(p, b.size(), b.align());
}
}
void
test04()
{
- std::pmr::unsynchronized_pool_resource r({256, 256});
+ __gnu_test::memory_resource test_mr;
+ std::pmr::unsynchronized_pool_resource r({256, 256}, &test_mr);
// Check alignment
void* p1 = r.allocate(2, 64);
VERIFY( (std::uintptr_t)p1 % 64 == 0 );
r.deallocate(p4, 2 * largest_pool, 1024);
}
+void
+test05()
+{
+ __gnu_test::memory_resource test_mr;
+ std::pmr::pool_options opts{};
+ opts.max_blocks_per_chunk = 1;
+ opts.largest_required_pool_block = 1;
+ std::pmr::unsynchronized_pool_resource r(opts, &test_mr);
+ opts = r.options();
+ // Test unpooled allocations
+ void** p = new void*[opts.largest_required_pool_block];
+ for (unsigned a : {64, 128, 256, 512})
+ {
+ for (unsigned i = 0; i < opts.largest_required_pool_block; ++i)
+ p[i] = r.allocate(i, a);
+ for (unsigned i = 0; i < opts.largest_required_pool_block; ++i)
+ r.deallocate(p[i], i, a);
+ }
+ delete[] p;
+}
+
+void
+test06()
+{
+ struct custom_mr : std::pmr::memory_resource
+ {
+ size_t expected_size = 0;
+ size_t expected_alignment = 0;
+
+ struct bad_size { };
+ struct bad_alignment { };
+
+ void* do_allocate(std::size_t b, std::size_t a)
+ {
+ if (expected_size != 0)
+ {
+ if (b < expected_size)
+ throw bad_size();
+ else if (a != expected_alignment)
+ throw bad_alignment();
+ // Else just throw, don't try to allocate:
+ throw std::bad_alloc();
+ }
+
+ return std::pmr::new_delete_resource()->allocate(b, a);
+ }
+
+ void do_deallocate(void* p, std::size_t b, std::size_t a)
+ { std::pmr::new_delete_resource()->deallocate(p, b, a); }
+
+ bool do_is_equal(const memory_resource& r) const noexcept
+ { return false; }
+ };
+
+ custom_mr c;
+ std::pmr::unsynchronized_pool_resource r({1, 1}, &c);
+ std::pmr::pool_options opts = r.options();
+ const std::size_t largest_pool = opts.largest_required_pool_block;
+ const std::size_t large_alignment = 1024;
+ // Ensure allocations won't fit in pools:
+ VERIFY( largest_pool < large_alignment );
+
+ // Ensure the vector of large allocations has some capacity
+ // and won't need to reallocate:
+ r.deallocate(r.allocate(largest_pool + 1, 1), largest_pool + 1, 1);
+
+ // Try allocating various very large sizes and ensure the size requested
+ // from the upstream allocator is at least as large as needed.
+ for (int i = 1; i < 64; ++i)
+ {
+ for (auto b : { -1, 0, 1, 3 })
+ {
+ std::size_t bytes = std::size_t(1) << i;
+ bytes += b;
+ c.expected_size = bytes;
+ c.expected_alignment = large_alignment;
+ try {
+ (void) r.allocate(bytes, large_alignment);
+ } catch (const std::bad_alloc&) {
+ // expect to catch bad_alloc
+ } catch (custom_mr::bad_size) {
+ VERIFY(false);
+ } catch (custom_mr::bad_alignment) {
+ VERIFY(false);
+ }
+ }
+ }
+}
+
int
main()
{
test02();
test03();
test04();
+ test05();
+ test06();
}
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