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