[UPDATE] Drop the MPI_Info window hints, measured to have no effect

Paired A/B at 448 ranks, three replicas per arm inside one allocation: with
no_locks=true the aggregated MPI_Win_create cost 1463 s against 1450 s
without it, the two ranges fully overlapping. A probe with MPI_Win_get_info
confirmed this Open MPI retains the hint, so the null result belongs to the
hint and not to a failed measurement; same_disp_unit was silently ignored.

Removes the cached MPI_Info handles and their helpers, and returns the four
PSCW win_create calls to MPI_INFO_NULL.

base/comm/internals/psi_dswapdata.F90

@@ -86,7 +86,7 @@ submodule (psi_d_comm_v_mod)  psi_d_swapdata_impl
   use psb_comm_schemes_mod, only: psb_comm_isend_irecv_, psb_comm_ineighbor_alltoallv_, &
       & psb_comm_persistent_ineighbor_alltoallv_, psb_comm_rma_pull_, psb_comm_rma_push_, &
       & psb_comm_handle_type
-  use psb_comm_rma_mod, only: psb_comm_rma_handle, psb_comm_rma_get_wininfo
+  use psb_comm_rma_mod, only: psb_comm_rma_handle
   use psb_comm_factory_mod
 
 contains
@@ -1003,7 +1003,7 @@ contains
     class(psb_comm_handle_type), intent(inout)    :: comm_handle
     integer(psb_ipk_), intent(out)                :: info
 
-    integer(psb_mpk_) :: np, my_rank, iret, element_bytes, icomm, win_info
+    integer(psb_mpk_) :: np, my_rank, iret, element_bytes, icomm
     integer(psb_mpk_) :: proc_to_comm, prc_rank, recv_count, send_count, send_pos, recv_pos, list_pos
     integer(psb_mpk_) :: remote_base
     integer(kind=MPI_ADDRESS_KIND) :: remote_disp, exposed_bytes
@@ -1106,14 +1106,8 @@ contains
         if (.not. rma_handle%window_ready) then
           element_bytes = storage_size(y%combuf(1))/8
           exposed_bytes = int(size(y%combuf),kind=MPI_ADDRESS_KIND) * int(element_bytes,kind=MPI_ADDRESS_KIND)
-          ! no_locks: this path synchronizes with PSCW only, never with win_lock.
-          call psb_comm_rma_get_wininfo(win_info, .true., info)
-          if (info /= psb_success_) then
-            call psb_errpush(info,name)
-            goto 9999
-          end if
           call mpi_win_create(y%combuf, exposed_bytes, element_bytes, &
-               & win_info, ctxt%get_mpic(), rma_handle%win, iret)
+               & mpi_info_null, ctxt%get_mpic(), rma_handle%win, iret)
           if (iret /= mpi_success) then
             info = psb_err_mpi_error_
             call psb_errpush(info,name,m_err=(/iret/))
@@ -1233,7 +1227,7 @@ contains
     class(psb_comm_handle_type), intent(inout)  :: comm_handle
     integer(psb_ipk_), intent(out)              :: info
 
-    integer(psb_mpk_) :: np, my_rank, iret, element_bytes, icomm, win_info
+    integer(psb_mpk_) :: np, my_rank, iret, element_bytes, icomm
     integer(psb_mpk_) :: proc_to_comm, prc_rank, recv_count, send_count, send_pos, recv_pos, list_pos
     integer(psb_mpk_) :: remote_base
     integer(kind=MPI_ADDRESS_KIND) :: remote_disp, exposed_bytes
@@ -1334,14 +1328,8 @@ contains
         if (.not. rma_handle%window_ready) then
           element_bytes = storage_size(y%combuf(1))/8
           exposed_bytes = int(size(y%combuf),kind=MPI_ADDRESS_KIND) * int(element_bytes,kind=MPI_ADDRESS_KIND)
-          ! no_locks: this path synchronizes with PSCW only, never with win_lock.
-          call psb_comm_rma_get_wininfo(win_info, .true., info)
-          if (info /= psb_success_) then
-            call psb_errpush(info,name)
-            goto 9999
-          end if
           call mpi_win_create(y%combuf, exposed_bytes, element_bytes, &
-               & win_info, ctxt%get_mpic(), rma_handle%win, iret)
+               & mpi_info_null, ctxt%get_mpic(), rma_handle%win, iret)
           if (iret /= mpi_success) then
             info = psb_err_mpi_error_
             call psb_errpush(info,name,m_err=(/iret/))
@@ -2290,7 +2278,7 @@ end subroutine psi_dswap_neighbor_topology_multivect_persistent
     class(psb_comm_handle_type), intent(inout)    :: comm_handle
     integer(psb_ipk_), intent(out)                :: info
 
-    integer(psb_mpk_) :: np, my_rank, iret, element_bytes, icomm, n, win_info
+    integer(psb_mpk_) :: np, my_rank, iret, element_bytes, icomm, n
     integer(psb_mpk_) :: proc_to_comm, prc_rank, recv_count, send_count, send_pos, recv_pos, list_pos
     integer(psb_mpk_) :: remote_base
     integer(kind=MPI_ADDRESS_KIND) :: remote_disp, exposed_bytes
@@ -2390,14 +2378,8 @@ end subroutine psi_dswap_neighbor_topology_multivect_persistent
         if (.not. rma_handle%window_ready) then
           element_bytes = storage_size(y%combuf(1))/8
           exposed_bytes = int(size(y%combuf),kind=MPI_ADDRESS_KIND) * int(element_bytes,kind=MPI_ADDRESS_KIND)
-          ! no_locks: this path synchronizes with PSCW only, never with win_lock.
-          call psb_comm_rma_get_wininfo(win_info, .true., info)
-          if (info /= psb_success_) then
-            call psb_errpush(info,name)
-            goto 9999
-          end if
           call mpi_win_create(y%combuf, exposed_bytes, element_bytes, &
-               & win_info, ctxt%get_mpic(), rma_handle%win, iret)
+               & mpi_info_null, ctxt%get_mpic(), rma_handle%win, iret)
           if (iret /= mpi_success) then
             info = psb_err_mpi_error_
             call psb_errpush(info,name,m_err=(/iret/))
@@ -2510,7 +2492,7 @@ end subroutine psi_dswap_neighbor_topology_multivect_persistent
     class(psb_comm_handle_type), intent(inout)    :: comm_handle
     integer(psb_ipk_), intent(out)                :: info
 
-    integer(psb_mpk_) :: np, my_rank, iret, element_bytes, icomm, n, win_info
+    integer(psb_mpk_) :: np, my_rank, iret, element_bytes, icomm, n
     integer(psb_mpk_) :: proc_to_comm, prc_rank, recv_count, send_count, send_pos, recv_pos, list_pos
     integer(psb_mpk_) :: remote_base
     integer(kind=MPI_ADDRESS_KIND) :: remote_disp, exposed_bytes
@@ -2610,14 +2592,8 @@ end subroutine psi_dswap_neighbor_topology_multivect_persistent
         if (.not. rma_handle%window_ready) then
           element_bytes = storage_size(y%combuf(1))/8
           exposed_bytes = int(size(y%combuf),kind=MPI_ADDRESS_KIND) * int(element_bytes,kind=MPI_ADDRESS_KIND)
-          ! no_locks: this path synchronizes with PSCW only, never with win_lock.
-          call psb_comm_rma_get_wininfo(win_info, .true., info)
-          if (info /= psb_success_) then
-            call psb_errpush(info,name)
-            goto 9999
-          end if
           call mpi_win_create(y%combuf, exposed_bytes, element_bytes, &
-               & win_info, ctxt%get_mpic(), rma_handle%win, iret)
+               & mpi_info_null, ctxt%get_mpic(), rma_handle%win, iret)
           if (iret /= mpi_success) then
             info = psb_err_mpi_error_
             call psb_errpush(info,name,m_err=(/iret/))

base/modules/comm/comm_schemes/psb_comm_rma_mod.F90

@@ -15,23 +15,6 @@ module psb_comm_rma_mod
   include 'mpif.h'
 #endif
 
-  ! Hints attached to every window created by the one-sided schemes.
-  !
-  ! Given no info at all, the implementation has to stay ready for the general
-  ! case: a passive-target lock could arrive at any moment, and ranks could have
-  ! passed different displacement units. Staying ready is not free -- it costs
-  ! metadata exchanged among all ranks on each creation -- and creation is where
-  ! these schemes spend most of their time. The assertions below hold here and
-  ! cost nothing to make.
-  !
-  ! Deliberately NOT asserted: same_size. Halo buffers are sized by the local
-  ! halo, which differs from rank to rank, so that assertion would be false.
-  !
-  ! Cached for the life of the program: the hints never change, and building an
-  ! info object per window would add to the very cost this is meant to remove.
-  integer(psb_mpk_), private, save :: rma_wininfo_pscw = mpi_info_null
-  integer(psb_mpk_), private, save :: rma_wininfo_gen  = mpi_info_null
-
   type, extends(psb_comm_handle_type) :: psb_comm_rma_handle
     integer(psb_mpk_) :: win = mpi_win_null
     logical :: window_ready = .false.
@@ -68,51 +51,6 @@ module psb_comm_rma_mod
 
 contains
 
-  ! Return the MPI_Info to pass to mpi_win_create, building it on first use.
-  ! no_locks must be .true. only where the window is synchronized exclusively
-  ! with PSCW: it asserts that no passive-target epoch will ever be opened on
-  ! it, and a win_lock afterwards would be erroneous. Today that is the double
-  ! precision swapdata path; every other path still takes locks.
-  subroutine psb_comm_rma_get_wininfo(winfo, no_locks, info)
-    integer(psb_mpk_), intent(out) :: winfo
-    logical, intent(in) :: no_locks
-    integer(psb_ipk_), intent(out) :: info
-
-    info = psb_success_
-    if (no_locks) then
-      if (rma_wininfo_pscw == mpi_info_null) then
-        call psb_comm_rma_build_wininfo(rma_wininfo_pscw, .true., info)
-        if (info /= psb_success_) return
-      end if
-      winfo = rma_wininfo_pscw
-    else
-      if (rma_wininfo_gen == mpi_info_null) then
-        call psb_comm_rma_build_wininfo(rma_wininfo_gen, .false., info)
-        if (info /= psb_success_) return
-      end if
-      winfo = rma_wininfo_gen
-    end if
-  end subroutine psb_comm_rma_get_wininfo
-
-  subroutine psb_comm_rma_build_wininfo(winfo, no_locks, info)
-    integer(psb_mpk_), intent(out) :: winfo
-    logical, intent(in) :: no_locks
-    integer(psb_ipk_), intent(out) :: info
-    integer(psb_mpk_) :: iret
-
-    info  = psb_success_
-    winfo = mpi_info_null
-    call mpi_info_create(winfo, iret)
-    if (iret /= mpi_success) then
-      info  = psb_err_mpi_error_
-      winfo = mpi_info_null
-      return
-    end if
-    ! Every rank passes the size of one element of the same type.
-    call mpi_info_set(winfo, 'same_disp_unit', 'true', iret)
-    if (no_locks) call mpi_info_set(winfo, 'no_locks', 'true', iret)
-  end subroutine psb_comm_rma_build_wininfo
-
   subroutine psb_comm_rma_init(this, info)
     class(psb_comm_rma_handle), intent(inout) :: this
     integer(psb_ipk_), intent(out) :: info