118 lines
2.6 KiB
C++
118 lines
2.6 KiB
C++
#ifndef BLOCK_CACHE_IO_ENGINE_H
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#define BLOCK_CACHE_IO_ENGINE_H
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#include "base/unique_handle.h"
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#include <boost/optional.hpp>
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#include <ctype.h>
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#include <set>
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#include <string>
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#include <libaio.h>
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//----------------------------------------------------------------
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namespace bcache {
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using sector_t = uint64_t;
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unsigned const SECTOR_SHIFT = 9;
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unsigned const PAGE_SIZE = 4096;
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// Virtual base class to aid unit testing
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class io_engine {
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public:
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enum mode {
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M_READ_ONLY,
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M_READ_WRITE
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};
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enum dir {
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D_READ,
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D_WRITE
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};
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enum sharing {
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EXCLUSIVE,
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SHARED
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};
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io_engine() {}
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virtual ~io_engine() {}
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using handle = unsigned;
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virtual handle open_file(std::string const &path, mode m, sharing s = EXCLUSIVE) = 0;
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virtual void close_file(handle h) = 0;
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// returns false if there are insufficient resources to
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// queue the IO
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virtual bool issue_io(handle h, dir d, sector_t b, sector_t e, void *data, unsigned context) = 0;
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// returns (success, context)
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using wait_result = std::pair<bool, unsigned>;
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virtual boost::optional<wait_result> wait() = 0;
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virtual boost::optional<wait_result> wait(unsigned µsec) = 0;
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private:
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io_engine(io_engine const &) = delete;
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io_engine &operator =(io_engine const &) = delete;
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};
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//--------------------------------
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class control_block_set {
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public:
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control_block_set(unsigned nr);
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iocb *alloc(unsigned context);
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void free(iocb *);
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unsigned context(iocb *) const;
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private:
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struct cblock {
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unsigned context;
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struct iocb cb;
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};
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std::set<unsigned> free_cbs_;
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std::vector<cblock> cbs_;
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};
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//----------------
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class aio_engine : public io_engine {
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public:
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// max_io is the maximum nr of concurrent ios expected
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aio_engine(unsigned max_io);
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~aio_engine();
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using handle = unsigned;
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virtual handle open_file(std::string const &path, mode m, sharing s = EXCLUSIVE);
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virtual void close_file(handle h);
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// Returns false if queueing the io failed
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virtual bool issue_io(handle h, dir d, sector_t b, sector_t e, void *data, unsigned context);
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virtual boost::optional<wait_result> wait();
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virtual boost::optional<wait_result> wait(unsigned µsec);
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private:
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static struct timespec micro_to_ts(unsigned micro);
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static unsigned ts_to_micro(timespec const &ts);
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boost::optional<io_engine::wait_result> wait_(timespec *ts);
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std::list<base::unique_fd> descriptors_;
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io_context_t aio_context_;
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control_block_set cbs_;
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aio_engine(io_engine const &) = delete;
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aio_engine &operator =(io_engine const &) = delete;
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};
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}
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//----------------------------------------------------------------
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#endif
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