ClickHouse/src/Common/Arena.h

322 lines
10 KiB
C++

#pragma once
#include <string.h>
#include <memory>
#include <vector>
#include <boost/noncopyable.hpp>
#if __has_include(<sanitizer/asan_interface.h>)
# include <sanitizer/asan_interface.h>
#endif
#include <Core/Defines.h>
#include <Common/memcpySmall.h>
#include <Common/ProfileEvents.h>
#include <Common/Allocator.h>
namespace ProfileEvents
{
extern const Event ArenaAllocChunks;
extern const Event ArenaAllocBytes;
}
namespace DB
{
/** Memory pool to append something. For example, short strings.
* Usage scenario:
* - put lot of strings inside pool, keep their addresses;
* - addresses remain valid during lifetime of pool;
* - at destruction of pool, all memory is freed;
* - memory is allocated and freed by large chunks;
* - freeing parts of data is not possible (but look at ArenaWithFreeLists if you need);
*/
class Arena : private boost::noncopyable
{
private:
/// Padding allows to use 'memcpySmallAllowReadWriteOverflow15' instead of 'memcpy'.
static constexpr size_t pad_right = 15;
/// Contiguous chunk of memory and pointer to free space inside it. Member of single-linked list.
struct alignas(16) Chunk : private Allocator<false> /// empty base optimization
{
char * begin;
char * pos;
char * end; /// does not include padding.
Chunk * prev;
Chunk(size_t size_, Chunk * prev_)
{
ProfileEvents::increment(ProfileEvents::ArenaAllocChunks);
ProfileEvents::increment(ProfileEvents::ArenaAllocBytes, size_);
begin = reinterpret_cast<char *>(Allocator<false>::alloc(size_));
pos = begin;
end = begin + size_ - pad_right;
prev = prev_;
ASAN_POISON_MEMORY_REGION(begin, size_);
}
~Chunk()
{
/// We must unpoison the memory before returning to the allocator,
/// because the allocator might not have asan integration, and the
/// memory would stay poisoned forever. If the allocator supports
/// asan, it will correctly poison the memory by itself.
ASAN_UNPOISON_MEMORY_REGION(begin, size());
Allocator<false>::free(begin, size());
if (prev)
delete prev;
}
size_t size() const { return end + pad_right - begin; }
size_t remaining() const { return end - pos; }
};
size_t growth_factor;
size_t linear_growth_threshold;
/// Last contiguous chunk of memory.
Chunk * head;
size_t size_in_bytes;
static size_t roundUpToPageSize(size_t s)
{
return (s + 4096 - 1) / 4096 * 4096;
}
/// If chunks size is less than 'linear_growth_threshold', then use exponential growth, otherwise - linear growth
/// (to not allocate too much excessive memory).
size_t nextSize(size_t min_next_size) const
{
size_t size_after_grow = 0;
if (head->size() < linear_growth_threshold)
{
size_after_grow = std::max(min_next_size, head->size() * growth_factor);
}
else
{
// allocContinue() combined with linear growth results in quadratic
// behavior: we append the data by small amounts, and when it
// doesn't fit, we create a new chunk and copy all the previous data
// into it. The number of times we do this is directly proportional
// to the total size of data that is going to be serialized. To make
// the copying happen less often, round the next size up to the
// linear_growth_threshold.
size_after_grow = ((min_next_size + linear_growth_threshold - 1)
/ linear_growth_threshold) * linear_growth_threshold;
}
assert(size_after_grow >= min_next_size);
return roundUpToPageSize(size_after_grow);
}
/// Add next contiguous chunk of memory with size not less than specified.
void NO_INLINE addChunk(size_t min_size)
{
head = new Chunk(nextSize(min_size + pad_right), head);
size_in_bytes += head->size();
}
friend class ArenaAllocator;
template <size_t> friend class AlignedArenaAllocator;
public:
Arena(size_t initial_size_ = 4096, size_t growth_factor_ = 2, size_t linear_growth_threshold_ = 128 * 1024 * 1024)
: growth_factor(growth_factor_), linear_growth_threshold(linear_growth_threshold_),
head(new Chunk(initial_size_, nullptr)), size_in_bytes(head->size())
{
}
~Arena()
{
delete head;
}
/// Get piece of memory, without alignment.
char * alloc(size_t size)
{
if (unlikely(head->pos + size > head->end))
addChunk(size);
char * res = head->pos;
head->pos += size;
ASAN_UNPOISON_MEMORY_REGION(res, size + pad_right);
return res;
}
/// Get piece of memory with alignment
char * alignedAlloc(size_t size, size_t alignment)
{
do
{
void * head_pos = head->pos;
size_t space = head->end - head->pos;
auto res = static_cast<char *>(std::align(alignment, size, head_pos, space));
if (res)
{
head->pos = static_cast<char *>(head_pos);
head->pos += size;
ASAN_UNPOISON_MEMORY_REGION(res, size + pad_right);
return res;
}
addChunk(size + alignment);
} while (true);
}
template <typename T>
T * alloc()
{
return reinterpret_cast<T *>(alignedAlloc(sizeof(T), alignof(T)));
}
/** Rollback just performed allocation.
* Must pass size not more that was just allocated.
* Return the resulting head pointer, so that the caller can assert that
* the allocation it intended to roll back was indeed the last one.
*/
void * rollback(size_t size)
{
head->pos -= size;
ASAN_POISON_MEMORY_REGION(head->pos, size + pad_right);
return head->pos;
}
/** Begin or expand a contiguous range of memory.
* 'range_start' is the start of range. If nullptr, a new range is
* allocated.
* If there is no space in the current chunk to expand the range,
* the entire range is copied to a new, bigger memory chunk, and the value
* of 'range_start' is updated.
* If the optional 'start_alignment' is specified, the start of range is
* kept aligned to this value.
*
* NOTE This method is usable only for the last allocation made on this
* Arena. For earlier allocations, see 'realloc' method.
*/
char * allocContinue(size_t additional_bytes, char const *& range_start,
size_t start_alignment = 0)
{
/*
* Allocating zero bytes doesn't make much sense. Also, a zero-sized
* range might break the invariant that the range begins at least before
* the current chunk end.
*/
assert(additional_bytes > 0);
if (!range_start)
{
// Start a new memory range.
char * result = start_alignment
? alignedAlloc(additional_bytes, start_alignment)
: alloc(additional_bytes);
range_start = result;
return result;
}
// Extend an existing memory range with 'additional_bytes'.
// This method only works for extending the last allocation. For lack of
// original size, check a weaker condition: that 'begin' is at least in
// the current Chunk.
assert(range_start >= head->begin);
assert(range_start < head->end);
if (head->pos + additional_bytes <= head->end)
{
// The new size fits into the last chunk, so just alloc the
// additional size. We can alloc without alignment here, because it
// only applies to the start of the range, and we don't change it.
return alloc(additional_bytes);
}
// New range doesn't fit into this chunk, will copy to a new one.
//
// Note: among other things, this method is used to provide a hack-ish
// implementation of realloc over Arenas in ArenaAllocators. It wastes a
// lot of memory -- quadratically so when we reach the linear allocation
// threshold. This deficiency is intentionally left as is, and should be
// solved not by complicating this method, but by rethinking the
// approach to memory management for aggregate function states, so that
// we can provide a proper realloc().
const size_t existing_bytes = head->pos - range_start;
const size_t new_bytes = existing_bytes + additional_bytes;
const char * old_range = range_start;
char * new_range = start_alignment
? alignedAlloc(new_bytes, start_alignment)
: alloc(new_bytes);
memcpy(new_range, old_range, existing_bytes);
range_start = new_range;
return new_range + existing_bytes;
}
/// NOTE Old memory region is wasted.
char * realloc(const char * old_data, size_t old_size, size_t new_size)
{
char * res = alloc(new_size);
if (old_data)
{
memcpy(res, old_data, old_size);
ASAN_POISON_MEMORY_REGION(old_data, old_size);
}
return res;
}
char * alignedRealloc(const char * old_data, size_t old_size, size_t new_size, size_t alignment)
{
char * res = alignedAlloc(new_size, alignment);
if (old_data)
{
memcpy(res, old_data, old_size);
ASAN_POISON_MEMORY_REGION(old_data, old_size);
}
return res;
}
/// Insert string without alignment.
const char * insert(const char * data, size_t size)
{
char * res = alloc(size);
memcpy(res, data, size);
return res;
}
const char * alignedInsert(const char * data, size_t size, size_t alignment)
{
char * res = alignedAlloc(size, alignment);
memcpy(res, data, size);
return res;
}
/// Size of chunks in bytes.
size_t size() const
{
return size_in_bytes;
}
/// Bad method, don't use it -- the chunks are not your business, the entire
/// purpose of the arena code is to manage them for you, so if you find
/// yourself having to use this method, probably you're doing something wrong.
size_t remainingSpaceInCurrentChunk() const
{
return head->remaining();
}
};
using ArenaPtr = std::shared_ptr<Arena>;
using Arenas = std::vector<ArenaPtr>;
}