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/ge25519_isneutral.c

@@ -0,0 +1,9 @@
+#include "fe25519.h"
+#include "ge25519.h"
+
+int ge25519_isneutral_vartime(const ge25519_p3 *p)
+{
+  if(!fe25519_iszero_vartime(&p->x)) return 0;
+  if(!fe25519_iseq_vartime(&p->y, &p->z)) return 0;
+  return 1;
+}