I got the same result as with events.
=====Test1=====
Discriminator backward :  0.0120358 s
Discriminator backward :  0.0067697 s
Hessian vector product :  0.0130763 s
=====Test2=====
Discriminator backward :  0.0188158 s
Discriminator backward :  0.0291374 s
Hessian vector product :  1.1108479 s