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openmpi/ompi/mca/coll/sm/coll_sm_bcast.c
Jeff Squyres 1ef988c3d9 A slight optimization: no longer call sched_yield() when polling for
shmem progress (or the Windows equiv).  Instead, poll hard on the
condition, but periocially call opal_progress().  This allows
badly-formed apps (e.g., the ibm test communicator/bsend_free) to
actually complete.

To be clear, there are far too many apps out there that assume that
MPI collectives will actually progress the rest of MPI.  I don't like
putting in a feature to enable broken apps, but I have a dim
recollection of this issue coming up before (apps "hanging" when
testing the sm coll because they assumed that calling collectives
would trigger other MPI progress).  Rather than have people claim that
OMPI is broken, I prefer to put in this "workaround".  :-(

Indeed, the bsend_free test ''may'' be coded that way for exactly that
reason...?  I don't remember offhand...

This commit was SVN r21984.
2009-09-21 22:20:44 +00:00

255 строки
9.9 KiB
C

/*
* Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
* University Research and Technology
* Corporation. All rights reserved.
* Copyright (c) 2004-2005 The University of Tennessee and The University
* of Tennessee Research Foundation. All rights
* reserved.
* Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
* University of Stuttgart. All rights reserved.
* Copyright (c) 2004-2005 The Regents of the University of California.
* All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*/
/** @file */
#include "ompi_config.h"
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#include "opal/datatype/opal_convertor.h"
#include "ompi/constants.h"
#include "ompi/communicator/communicator.h"
#include "ompi/datatype/ompi_datatype.h"
#include "ompi/mca/coll/coll.h"
#include "opal/sys/atomic.h"
#include "coll_sm.h"
/**
* Shared memory broadcast.
*
* For the root, the general algorithm is to wait for a set of
* segments to become available. Once it is, the root claims the set
* by writing the current operation number and the number of processes
* using the set to the flag. The root then loops over the set of
* segments; for each segment, it copies a fragment of the user's
* buffer into the shared data segment and then writes the data size
* into its childrens' control buffers. The process is repeated until
* all fragments have been written.
*
* For non-roots, for each set of buffers, they wait until the current
* operation number appears in the in-use flag (i.e., written by the
* root). Then for each segment, they wait for a nonzero to appear
* into their control buffers. If they have children, they copy the
* data from their parent's shared data segment into their shared data
* segment, and write the data size into each of their childrens'
* control buffers. They then copy the data from their shared [local]
* data segment into the user's output buffer. The process is
* repeated until all fragments have been received. If they do not
* have children, they copy the data directly from the parent's shared
* data segment into the user's output buffer.
*/
int mca_coll_sm_bcast_intra(void *buff, int count,
struct ompi_datatype_t *datatype, int root,
struct ompi_communicator_t *comm,
mca_coll_base_module_t *module)
{
struct iovec iov;
mca_coll_sm_module_t *sm_module = (mca_coll_sm_module_t*) module;
mca_coll_sm_comm_t *data = sm_module->sm_comm_data;
int i, ret, rank, size, num_children, src_rank;
int flag_num, segment_num, max_segment_num;
int parent_rank;
size_t total_size, max_data, bytes;
mca_coll_sm_in_use_flag_t *flag;
opal_convertor_t convertor;
mca_coll_sm_tree_node_t *me, *parent, **children;
mca_coll_sm_data_index_t *index;
/* Setup some identities */
rank = ompi_comm_rank(comm);
size = ompi_comm_size(comm);
OBJ_CONSTRUCT(&convertor, opal_convertor_t);
iov.iov_len = mca_coll_sm_component.sm_fragment_size;
bytes = 0;
me = &data->mcb_tree[(rank + size - root) % size];
parent = me->mcstn_parent;
children = me->mcstn_children;
num_children = me->mcstn_num_children;
/* Only have one top-level decision as to whether I'm the root or
not. Do this at the slight expense of repeating a little logic
-- but it's better than a conditional branch in every loop
iteration. */
/*********************************************************************
* Root
*********************************************************************/
if (root == rank) {
/* The root needs a send convertor to pack from the user's
buffer to shared memory */
if (OMPI_SUCCESS !=
(ret =
opal_convertor_copy_and_prepare_for_send(ompi_mpi_local_convertor,
&(datatype->super),
count,
buff,
0,
&convertor))) {
return ret;
}
opal_convertor_get_packed_size(&convertor, &total_size);
/* Main loop over sending fragments */
do {
flag_num = (data->mcb_operation_count++ %
mca_coll_sm_component.sm_comm_num_in_use_flags);
FLAG_SETUP(flag_num, flag, data);
FLAG_WAIT_FOR_IDLE(flag, bcast_root_label);
FLAG_RETAIN(flag, size - 1, data->mcb_operation_count - 1);
/* Loop over all the segments in this set */
segment_num =
flag_num * mca_coll_sm_component.sm_segs_per_inuse_flag;
max_segment_num =
(flag_num + 1) * mca_coll_sm_component.sm_segs_per_inuse_flag;
do {
index = &(data->mcb_data_index[segment_num]);
/* Copy the fragment from the user buffer to my fragment
in the current segment */
max_data = mca_coll_sm_component.sm_fragment_size;
COPY_FRAGMENT_IN(convertor, index, rank, iov, max_data);
bytes += max_data;
/* Wait for the write to absolutely complete */
opal_atomic_wmb();
/* Tell my children that this fragment is ready */
PARENT_NOTIFY_CHILDREN(children, num_children, index,
max_data);
++segment_num;
} while (bytes < total_size && segment_num < max_segment_num);
} while (bytes < total_size);
}
/*********************************************************************
* Non-root
*********************************************************************/
else {
/* Non-root processes need a receive convertor to unpack from
shared mmory to the user's buffer */
if (OMPI_SUCCESS !=
(ret =
opal_convertor_copy_and_prepare_for_recv(ompi_mpi_local_convertor,
&(datatype->super),
count,
buff,
0,
&convertor))) {
return ret;
}
opal_convertor_get_packed_size(&convertor, &total_size);
/* Loop over receiving (and possibly re-sending) the
fragments */
do {
flag_num = (data->mcb_operation_count %
mca_coll_sm_component.sm_comm_num_in_use_flags);
/* Wait for the root to mark this set of segments as
ours */
FLAG_SETUP(flag_num, flag, data);
FLAG_WAIT_FOR_OP(flag, data->mcb_operation_count, bcast_nonroot_label1);
++data->mcb_operation_count;
/* Loop over all the segments in this set */
segment_num =
flag_num * mca_coll_sm_component.sm_segs_per_inuse_flag;
max_segment_num =
(flag_num + 1) * mca_coll_sm_component.sm_segs_per_inuse_flag;
do {
/* Pre-calculate some values */
parent_rank = (parent->mcstn_id + root) % size;
index = &(data->mcb_data_index[segment_num]);
/* Wait for my parent to tell me that the segment is ready */
CHILD_WAIT_FOR_NOTIFY(rank, index, max_data, bcast_nonroot_label2);
/* If I have children, send the data to them */
if (num_children > 0) {
/* Copy the fragment from the parent's portion in
the segment to my portion in the segment. */
COPY_FRAGMENT_BETWEEN(parent_rank, rank, index, max_data);
/* Wait for the write to absolutely complete */
opal_atomic_wmb();
/* Tell my children that this fragment is ready */
PARENT_NOTIFY_CHILDREN(children, num_children, index,
max_data);
/* Set the "copy from buffer" to be my local
segment buffer so that we don't potentially
incur a non-local memory copy from the parent's
fan out data segment [again] when copying to
the user's buffer */
src_rank = rank;
}
/* If I don't have any children, set the "copy from
buffer" to be my parent's fan out segment to copy
directly from my parent */
else {
src_rank = parent_rank;
}
/* Copy to my output buffer */
max_data = mca_coll_sm_component.sm_fragment_size;
COPY_FRAGMENT_OUT(convertor, src_rank, index, iov, max_data);
bytes += max_data;
++segment_num;
} while (bytes < total_size && segment_num < max_segment_num);
/* Wait for all copy-out writes to complete before I say
I'm done with the segments */
opal_atomic_wmb();
/* We're finished with this set of segments */
FLAG_RELEASE(flag);
} while (bytes < total_size);
}
/* Kill the convertor */
OBJ_DESTRUCT(&convertor);
/* All done */
return OMPI_SUCCESS;
}