Commit 0ad607d6 authored by Nick Mathewson's avatar Nick Mathewson 🤹
Browse files

Faster chan_circid_entry_hash implementation 

Since this is critical-path, let's tune the value we pass to
csiphash a little so it fits into one whole round.
parent 8127f4db

src/or/circuitlist.c

+9 −8
Original line number Diff line number Diff line
@@ -76,14 +76,15 @@ chan_circid_entries_eq_(chan_circid_circuit_map_t *a, 
static INLINE unsigned int

chan_circid_entry_hash_(chan_circid_circuit_map_t *a)

{

  struct {

    void *chan;

    circid_t circid;

  } s;

  memset(&s, 0, sizeof(s));

  s.chan = a->chan;

  s.circid = a->circ_id;

  return (unsigned) siphash24g(&s, sizeof(s));

  /* Try to squeze the siphash input into 8 bytes to save any extra siphash

   * rounds.  This hash function is in the critical path. */

  uintptr_t chan = (uintptr_t) (void*) a->chan;

  uint32_t array[2];

  array[0] = a->circ_id;

  /* The low bits of the channel pointer are uninteresting, since the channel

   * is a pretty big structure. */

  array[1] = (uint32_t) (chan >> 6);

  return (unsigned) siphash24g(array, sizeof(array));

}



/** Map from [chan,circid] to circuit. */