Use X64 ASM ed25519 signatures on Linux/x64, which are about 10X faster. Will matter a lot for network controllers, not so much for other things.

ext/ed25519-amd64-asm/sc25519_window4.c

@@ -0,0 +1,27 @@
+#include "sc25519.h"
+
+void sc25519_window4(signed char r[64], const sc25519 *s)
+{
+  char carry;
+  int i;
+  for(i=0;i<16;i++)
+    r[i] = (s->v[0] >> (4*i)) & 15;
+  for(i=0;i<16;i++)
+    r[i+16] = (s->v[1] >> (4*i)) & 15;
+  for(i=0;i<16;i++)
+    r[i+32] = (s->v[2] >> (4*i)) & 15;
+  for(i=0;i<16;i++)
+    r[i+48] = (s->v[3] >> (4*i)) & 15;
+
+  /* Making it signed */
+  carry = 0;
+  for(i=0;i<63;i++)
+  {
+    r[i] += carry;
+    r[i+1] += r[i] >> 4;
+    r[i] &= 15;
+    carry = r[i] >> 3;
+    r[i] -= carry << 4;
+  }
+  r[63] += carry;
+}