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/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
/*
* Copyright (c) 2004-2007 The Trustees of Indiana University and Indiana
* University Research and Technology
* Corporation. All rights reserved.
* Copyright (c) 2004-2009 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 (c) 2006-2007 Voltaire. All rights reserved.
* Copyright (c) 2009-2010 Cisco Systems, Inc. All rights reserved.
* Copyright (c) 2010-2018 Los Alamos National Security, LLC.
* All rights reserved.
* Copyright (c) 2020 Google, LLC. All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*/
/**
* @file
*/
#ifndef MCA_BTL_SM_FIFO_H
#define MCA_BTL_SM_FIFO_H
#include "opal_config.h"
#include "opal/mca/btl/sm/btl_sm_fbox.h"
#include "opal/mca/btl/sm/btl_sm_types.h"
#include "opal/mca/btl/sm/btl_sm_virtual.h"
#define sm_item_compare_exchange(x, y, z) \
opal_atomic_compare_exchange_strong_ptr((opal_atomic_intptr_t *) (x), (intptr_t *) (y), \
(intptr_t)(z))
#define SM_FIFO_FREE ((fifo_value_t) -2)
/*
* Shared Memory FIFOs
*
* The FIFO is implemented as a linked list of frag headers. The fifo has multiple
* producers and a single consumer (in the single thread case) so the tail needs
* to be modified by an atomic or protected by a atomic lock.
*
* Since the frags live in shared memory that is mapped differently into
* each address space, the head and tail pointers are relative (each process must
* add its own offset).
*
* We introduce some padding at the end of the structure but it is probably unnecessary.
*/
/* large enough to ensure the fifo is on its own cache line */
#define MCA_BTL_SM_FIFO_SIZE 128
/**
* sm_fifo_read:
*
* @brief reads a single fragment from a local fifo
*
* @param[inout] fifo - FIFO to read from
* @param[out] ep - returns the endpoint the fifo element was read from
*
* @returns a fragment header or NULL
*
* This function does not currently support multiple readers.
*/
static inline mca_btl_sm_hdr_t *sm_fifo_read(sm_fifo_t *fifo, struct mca_btl_base_endpoint_t **ep)
{
mca_btl_sm_hdr_t *hdr;
fifo_value_t value;
if (SM_FIFO_FREE == fifo->fifo_head) {
return NULL;
}
opal_atomic_rmb();
value = fifo->fifo_head;
*ep = &mca_btl_sm_component.endpoints[value >> MCA_BTL_SM_OFFSET_BITS];
hdr = (mca_btl_sm_hdr_t *) relative2virtual(value);
fifo->fifo_head = SM_FIFO_FREE;
assert(hdr->next != value);
if (OPAL_UNLIKELY(SM_FIFO_FREE == hdr->next)) {
opal_atomic_rmb();
if (!sm_item_compare_exchange(&fifo->fifo_tail, &value, SM_FIFO_FREE)) {
while (SM_FIFO_FREE == hdr->next) {
opal_atomic_rmb();
}
fifo->fifo_head = hdr->next;
}
} else {
fifo->fifo_head = hdr->next;
}
opal_atomic_wmb();
return hdr;
}
static inline void sm_fifo_init(sm_fifo_t *fifo)
{
/* due to a compiler bug in Oracle C 5.15 the following line was broken into two. Not
* ideal but oh well. See #5814 */
/* fifo->fifo_head = fifo->fifo_tail = SM_FIFO_FREE; */
fifo->fifo_head = SM_FIFO_FREE;
fifo->fifo_tail = SM_FIFO_FREE;
fifo->fbox_available = mca_btl_sm_component.fbox_max;
mca_btl_sm_component.my_fifo = fifo;
}
static inline void sm_fifo_write(sm_fifo_t *fifo, fifo_value_t value)
{
fifo_value_t prev;
opal_atomic_wmb();
prev = opal_atomic_swap_ptr(&fifo->fifo_tail, value);
opal_atomic_rmb();
assert(prev != value);
if (OPAL_LIKELY(SM_FIFO_FREE != prev)) {
mca_btl_sm_hdr_t *hdr = (mca_btl_sm_hdr_t *) relative2virtual(prev);
hdr->next = value;
} else {
fifo->fifo_head = value;
}
opal_atomic_wmb();
}
/**
* sm_fifo_write_ep:
*
* @brief write a frag (relative to this process' base) to another rank's fifo
*
* @param[in] hdr - fragment header to write
* @param[in] ep - endpoint to write the fragment to
*
* This function is used to send a fragment to a remote peer. {hdr} must belong
* to the current process.
*/
static inline bool sm_fifo_write_ep(mca_btl_sm_hdr_t *hdr, struct mca_btl_base_endpoint_t *ep)
{
fifo_value_t rhdr = virtual2relative((char *) hdr);
if (ep->fbox_out.buffer) {
/* if there is a fast box for this peer then use the fast box to send the fragment header.
* this is done to ensure fragment ordering */
opal_atomic_wmb();
return mca_btl_sm_fbox_sendi(ep, 0xfe, &rhdr, sizeof(rhdr), NULL, 0);
}
mca_btl_sm_try_fbox_setup(ep, hdr);
hdr->next = SM_FIFO_FREE;
sm_fifo_write(ep->fifo, rhdr);
return true;
}
/**
* sm_fifo_write_back:
*
* @brief write a frag (relative to the remote process' base) to the remote fifo
*
* @param[in] hdr - fragment header to write
* @param[in] ep - endpoint the fragment belongs to
*
* This function is used to return a fragment to the sending process. It differs from
* sm_fifo_write_ep in that it uses the {ep} to produce the relative address.
*/
static inline void sm_fifo_write_back(mca_btl_sm_hdr_t *hdr, struct mca_btl_base_endpoint_t *ep)
{
hdr->next = SM_FIFO_FREE;
sm_fifo_write(ep->fifo, virtual2relativepeer(ep, (char *) hdr));
}
#endif /* MCA_BTL_SM_FIFO_H */
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