Dynamic windows (2a767a40) and the window pool (a3249c50) are kept in
history as measured negative results: no gain on window creation,
MPI_Get 49x slower, and a remote-access crash at 448 ranks. Back to
mpi_win_create, now with cached MPI_Info handles: same_disp_unit=true
always, no_locks=true only on the PSCW path in psi_dswapdata, the one
file where no passive-target call survives.
Validated at 8 ranks: psb_d_comm_test 9/9, and the AMG driver converges
in the same iterations to the same residual on all five schemes.
Stack-1
d82668259e