Support multi-threaded compression in COW v3 (6687cb65) · Commits · e / os / android_system_core

fs_mgr/libsnapshot/libsnapshot_cow/writer_v3.cpp

+100 −19

Original line number	Diff line number	Diff line
		@@ -34,6 +34,7 @@
		#include <zlib.h>

		#include <fcntl.h>
		#include <libsnapshot/cow_compress.h>
		#include <libsnapshot_cow/parser_v3.h>
		#include <linux/fs.h>
		#include <sys/ioctl.h>
		@@ -55,11 +56,35 @@ static_assert(sizeof(off_t) == sizeof(uint64_t));

		using android::base::unique_fd;

		// Divide \|x\| by \|y\| and round up to the nearest integer.
		constexpr uint64_t DivRoundUp(uint64_t x, uint64_t y) {
		return (x + y - 1) / y;
		}

		CowWriterV3::CowWriterV3(const CowOptions& options, unique_fd&& fd)
		: CowWriterBase(options, std::move(fd)), batch_size_(std::max<size_t>(options.cluster_ops, 1)) {
		SetupHeaders();
		}

		void CowWriterV3::InitWorkers() {
		if (num_compress_threads_ <= 1) {
		LOG_INFO << "Not creating new threads for compression.";
		return;
		}
		compress_threads_.reserve(num_compress_threads_);
		compress_threads_.clear();
		threads_.reserve(num_compress_threads_);
		threads_.clear();
		for (size_t i = 0; i < num_compress_threads_; i++) {
		std::unique_ptr<ICompressor> compressor =
		ICompressor::Create(compression_, header_.block_size);
		auto&& wt = compress_threads_.emplace_back(
		std::make_unique<CompressWorker>(std::move(compressor), header_.block_size));
		threads_.emplace_back(std::thread([wt = wt.get()]() { wt->RunThread(); }));
		}
		LOG(INFO) << num_compress_threads_ << " thread used for compression";
		}

		void CowWriterV3::SetupHeaders() {
		header_ = {};
		header_.prefix.magic = kCowMagicNumber;
		@@ -135,10 +160,24 @@ bool CowWriterV3::ParseOptions() {
		} else {
		LOG(INFO) << "Batch writes: disabled";
		}
		if (android::base::GetBoolProperty("ro.virtual_ab.compression.threads", false) &&
		options_.num_compress_threads) {
		num_compress_threads_ = options_.num_compress_threads;
		}
		InitWorkers();
		return true;
		}

		CowWriterV3::~CowWriterV3() {}
		CowWriterV3::~CowWriterV3() {
		for (const auto& t : compress_threads_) {
		t->Finalize();
		}
		for (auto& t : threads_) {
		if (t.joinable()) {
		t.join();
		}
		}
		}

		bool CowWriterV3::Initialize(std::optional<uint64_t> label) {
		if (!InitFd() \|\| !ParseOptions()) {
		@@ -289,19 +328,24 @@ bool CowWriterV3::EmitBlocks(uint64_t new_block_start, const void* data, size_t
		<< " but compressor is uninitialized.";
		return false;
		}
		const auto bytes = reinterpret_cast<const uint8_t*>(data);
		const size_t num_blocks = (size / header_.block_size);

		for (size_t i = 0; i < num_blocks;) {
		const auto blocks_to_write =
		std::min<size_t>(batch_size_ - cached_data_.size(), num_blocks - i);
		size_t compressed_bytes = 0;
		auto&& blocks = CompressBlocks(blocks_to_write, bytes + header_.block_size * i);
		if (blocks.size() != blocks_to_write) {
		LOG(ERROR) << "Failed to compress blocks " << new_block_start + i << ", "
		<< blocks_to_write << ", actual number of blocks received from compressor "
		<< blocks.size();
		return false;
		}
		for (size_t j = 0; j < blocks_to_write; j++) {
		const uint8_t* const iter =
		reinterpret_cast<const uint8_t>(data) + (header_.block_size (i + j));

		CowOperation& op = cached_ops_.emplace_back();
		auto& vec = data_vec_.emplace_back();
		auto& compressed_data = cached_data_.emplace_back();
		auto& compressed_data = cached_data_.emplace_back(std::move(blocks[j]));
		op.new_block = new_block_start + i + j;

		op.set_type(type);
		@@ -310,20 +354,6 @@ bool CowWriterV3::EmitBlocks(uint64_t new_block_start, const void* data, size_t
		} else {
		op.set_source(next_data_pos_ + compressed_bytes);
		}
		if (compression_.algorithm == kCowCompressNone) {
		compressed_data.resize(header_.block_size);
		} else {
		compressed_data = compressor_->Compress(iter, header_.block_size);
		if (compressed_data.empty()) {
		LOG(ERROR) << "Compression failed during EmitBlocks(" << new_block_start << ", "
		<< num_blocks << ");";
		return false;
		}
		}
		if (compressed_data.size() >= header_.block_size) {
		compressed_data.resize(header_.block_size);
		std::memcpy(compressed_data.data(), iter, header_.block_size);
		}
		vec = {.iov_base = compressed_data.data(), .iov_len = compressed_data.size()};
		op.data_length = vec.iov_len;
		compressed_bytes += op.data_length;
		@@ -443,6 +473,57 @@ bool CowWriterV3::FlushCacheOps() {
		return true;
		}

		std::vector<std::basic_string<uint8_t>> CowWriterV3::CompressBlocks(const size_t num_blocks,
		const void* data) {
		const size_t num_threads = (num_blocks == 1) ? 1 : num_compress_threads_;
		const size_t blocks_per_thread = DivRoundUp(num_blocks, num_threads);
		std::vector<std::basic_string<uint8_t>> compressed_buf;
		compressed_buf.clear();
		const uint8_t* const iter = reinterpret_cast<const uint8_t*>(data);
		if (compression_.algorithm == kCowCompressNone) {
		for (size_t i = 0; i < num_blocks; i++) {
		auto& buf = compressed_buf.emplace_back();
		buf.resize(header_.block_size);
		std::memcpy(buf.data(), iter + i * header_.block_size, header_.block_size);
		}
		return compressed_buf;
		}
		if (num_threads <= 1) {
		if (!CompressWorker::CompressBlocks(compressor_.get(), header_.block_size, data, num_blocks,
		&compressed_buf)) {
		return {};
		}
		} else {
		// Submit the blocks per thread. The retrieval of
		// compressed buffers has to be done in the same order.
		// We should not poll for completed buffers in a different order as the
		// buffers are tightly coupled with block ordering.
		for (size_t i = 0; i < num_threads; i++) {
		CompressWorker* worker = compress_threads_[i].get();
		const auto blocks_in_batch =
		std::min(num_blocks - i * blocks_per_thread, blocks_per_thread);
		worker->EnqueueCompressBlocks(iter + i * blocks_per_thread * header_.block_size,
		blocks_in_batch);
		}

		for (size_t i = 0; i < num_threads; i++) {
		CompressWorker* worker = compress_threads_[i].get();
		if (!worker->GetCompressedBuffers(&compressed_buf)) {
		return {};
		}
		}
		}
		for (size_t i = 0; i < num_blocks; i++) {
		auto& block = compressed_buf[i];
		if (block.size() >= header_.block_size) {
		block.resize(header_.block_size);
		std::memcpy(block.data(), iter + header_.block_size * i, header_.block_size);
		}
		}

		return compressed_buf;
		}

		bool CowWriterV3::WriteOperation(std::basic_string_view<CowOperationV3> ops,
		std::basic_string_view<struct iovec> data) {
		const auto total_data_size =

fs_mgr/libsnapshot/libsnapshot_cow/writer_v3.h

+6 −1

Original line number	Diff line number	Diff line
		@@ -16,6 +16,7 @@

		#include <android-base/logging.h>
		#include <string_view>
		#include <thread>
		#include <vector>

		#include "writer_base.h"
		@@ -51,12 +52,14 @@ class CowWriterV3 : public CowWriterBase {
		std::basic_string_view<struct iovec> data);
		bool EmitBlocks(uint64_t new_block_start, const void* data, size_t size, uint64_t old_block,
		uint16_t offset, CowOperationType type);
		bool CompressBlocks(size_t num_blocks, const void* data);
		bool CheckOpCount(size_t op_count);

		private:
		std::vector<std::basic_string<uint8_t>> CompressBlocks(const size_t num_blocks,
		const void* data);
		bool ReadBackVerification();
		bool FlushCacheOps();
		void InitWorkers();
		CowHeaderV3 header_{};
		CowCompression compression_;
		// in the case that we are using one thread for compression, we can store and re-use the same
		@@ -75,6 +78,8 @@ class CowWriterV3 : public CowWriterBase {
		std::vector<CowOperationV3> cached_ops_;
		std::vector<std::basic_string<uint8_t>> cached_data_;
		std::vector<struct iovec> data_vec_;

		std::vector<std::thread> threads_;
		};

		} // namespace snapshot