git.sesse.net Git - plocate/blob - io_uring_engine.h

   1 #ifndef IO_URING_ENGINE_H
   2 #define IO_URING_ENGINE_H 1
   3
   4 #include <functional>
   5 #include <queue>
   6 #include <stddef.h>
   7 #include <string_view>
   8 #include <sys/socket.h>
   9 #include <sys/types.h>
  10
  11 struct io_uring_sqe;
  12 #ifndef WITHOUT_URING
  13 #include <liburing.h>
  14 #endif
  15
  16 class IOUringEngine {
  17 public:
  18         IOUringEngine(size_t slop_bytes);
  19         void submit_read(int fd, size_t len, off_t offset, std::function<void(std::string_view)> cb);
  20
  21         // NOTE: We just do the stat() to get the data into the dentry cache for fast access,
  22         // or to check whether the file exists. Thus, the callback has only an OK/not OK boolean.
  23         void submit_stat(const char *path, std::function<void(bool ok)> cb);
  24         bool get_supports_stat() { return supports_stat; }
  25
  26         void finish();
  27         size_t get_waiting_reads() const { return pending_reads + queued_reads.size(); }
  28
  29 private:
  30 #ifndef WITHOUT_URING
  31         void submit_read_internal(io_uring_sqe *sqe, int fd, size_t len, off_t offset, std::function<void(std::string_view)> cb);
  32         void submit_stat_internal(io_uring_sqe *sqe, char *path, std::function<void(bool)> cb);
  33
  34         io_uring ring;
  35 #endif
  36         size_t pending_reads = 0;  // Number of requests we have going in the ring.
  37         bool using_uring, supports_stat = false;
  38         const size_t slop_bytes;
  39
  40         struct QueuedRead {
  41                 int fd;
  42                 size_t len;
  43                 off_t offset;
  44                 std::function<void(std::string_view)> cb;
  45         };
  46         std::queue<QueuedRead> queued_reads;
  47
  48         struct QueuedStat {
  49                 char *pathname;  // Owned by us.
  50                 std::function<void(bool)> cb;
  51         };
  52         std::queue<QueuedStat> queued_stats;
  53
  54         enum Op { OP_READ,
  55                   OP_STAT };
  56
  57         struct PendingRead {
  58                 Op op;
  59
  60                 std::function<void(std::string_view)> read_cb;
  61                 std::function<void(bool)> stat_cb;
  62
  63                 union {
  64                         struct {
  65                                 void *buf;
  66                                 size_t len;
  67
  68                                 // For re-submission.
  69                                 int fd;
  70                                 off_t offset;
  71                                 iovec iov;
  72                         } read;
  73                         struct {
  74                                 char *pathname;
  75                                 struct statx *buf;
  76                         } stat;
  77                 };
  78         };
  79
  80         // 256 simultaneous requests should be ample, for slow and fast media alike.
  81         static constexpr size_t queue_depth = 256;
  82 };
  83
  84 #endif  // !defined(IO_URING_ENGINE_H)