blis/addon/aocl_gemm/frame/threading/lpgemm_thread_utils.c

/*

   BLIS
   An object-based framework for developing high-performance BLAS-like
   libraries.

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   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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*/

#include "blis.h"
#include "lpgemm_thread_utils.h"

static bli_pthread_once_t once_check_lpgemm_thread_topo_init = BLIS_PTHREAD_ONCE_INIT;

static lpgemm_thread_attrs_t lpgemm_thread_attrs;

#ifdef BLIS_ENABLE_OPENMP

static void lpgemm_detect_thread_topo()
{
	int nt_max = omp_get_max_threads();
	int num_procs = omp_get_num_procs();

	if ( nt_max > num_procs )
	{
		// Over subscription of threads, no more work distr.
		return;
	}

	lpgemm_thread_attrs.tid_cnt = nt_max;
	lpgemm_thread_attrs.openmp_enabled = TRUE;

    // Allocating memory for pointers, to track thread-core(s) binding
    // by OpenMP. The pointers are also initialized to NULL, in case we
    // actually do not spawn nt_max number of threads in the subsequent
    // parallel region.
	int** thread_core_bind_list = NULL;
	int* adj_tid_cnt_for_core_grps = NULL;
	int* tid_cnt_for_core_grps = NULL;

	thread_core_bind_list = calloc( nt_max, sizeof( int* ) );
	if ( thread_core_bind_list == NULL )
	{
		goto err_handle;
	}

	// Launch max threads to determine the core bininding for all threads
	// within the omp team.
	#pragma omp parallel num_threads(nt_max)
	{
		int thread_num = omp_get_thread_num();
		int thread_place = omp_get_place_num();
		int place_num_procs = omp_get_place_num_procs( thread_place );

		// 1 extra int for storing num_procs value.
		thread_core_bind_list[thread_num] = malloc( ( place_num_procs + 1 ) * sizeof( int ) );
		if ( thread_core_bind_list[thread_num] != NULL )
		{
			thread_core_bind_list[thread_num][0] = place_num_procs;
			omp_get_place_proc_ids( thread_place, &thread_core_bind_list[thread_num][1] );
		}
	}

	// When SMT is on, this should be 16. Need a way to dynamically retrieve it.
	const int core_grp_size = 8;
	bool can_detect_topo = TRUE;

	lpgemm_thread_attrs.tid_core_grp_id_list = malloc( nt_max * sizeof( int ) );
	if ( lpgemm_thread_attrs.tid_core_grp_id_list == NULL )
	{
		goto err_handle;
	}

	// TIDs are assigned from 0 to nt_max - 1.
	// OpenMP for close distribution need not pin threads to sequential cores
	// in the presence of CCD architecture. Like tid 0-7 will be on core 0-7
	// but tid 8-15 could be on core 96-103. So just checking for increasing
	// core id for corresponding tid wont get accurate core group load.
	// GOMP_CPU_AFFINITY however assigns cores sequentially.
	for ( int ii = 0; ii < nt_max; ++ii )
	{
		lpgemm_thread_attrs.tid_core_grp_id_list[ii] = -1;
        // Identify the core(s) in which thread would be bound
        // In case the thread was never spawned, this code-section is skipped.
		if ( thread_core_bind_list[ii] != NULL)
		{
			// Wrap around the proc/core ids based on number of cores used.
			int st_core_grp_id =
			 ( thread_core_bind_list[ii][1] % num_procs ) / core_grp_size;
			lpgemm_thread_attrs.tid_core_grp_id_list[ii] = st_core_grp_id;
			for ( int jj = 1; jj < thread_core_bind_list[ii][0]; ++jj )
			{
				int cur_core_grp_id =
				 ( thread_core_bind_list[ii][jj + 1] % num_procs ) / core_grp_size;
				if ( cur_core_grp_id != st_core_grp_id )
				{
					// Core binding spanning across core groups,
					// cannot detect topo.
					can_detect_topo = FALSE;
					break;
				}
			}
		}
		else
		{
			// Thread was not spawned, cannot detect topo.
			// Break out of the current loop.
			can_detect_topo = FALSE;
			break;
		}
		// Check if the topo detection failed at any point.
		// If so, break out of the loop.
		if ( can_detect_topo == FALSE )
		{
			break;
		}
	}

	int num_core_grps = num_procs / core_grp_size;

	// Get count of core groups that are loaded and not loaded with adj ranks.
	// This will give an approximation for thread pin distribution.
	if ( can_detect_topo == TRUE )
	{
		// Allocate memory to track the thread counts for each core group.
		adj_tid_cnt_for_core_grps = calloc( num_core_grps, sizeof( int ) );
		tid_cnt_for_core_grps = calloc( num_core_grps, sizeof( int ) );
		if ( ( adj_tid_cnt_for_core_grps == NULL ) || ( tid_cnt_for_core_grps == NULL ) )
		{
			goto err_handle;
		}

		const int core_grp_loaded_thres = 3;
		int core_grp_adj_tid_thres_cnt = 0;
		int core_grp_adj_tid_cnt = 0;
		int core_grp_non_adj_tid_cnt = 0;

		int cur_core_grp_id = lpgemm_thread_attrs.tid_core_grp_id_list[0];
		tid_cnt_for_core_grps[cur_core_grp_id] += 1;

		for ( int ii = 1; ii < nt_max; ++ii )
		{
			if ( lpgemm_thread_attrs.tid_core_grp_id_list[ii] == cur_core_grp_id )
			{
				adj_tid_cnt_for_core_grps[cur_core_grp_id] += 1;
			}
			else
			{
				cur_core_grp_id = lpgemm_thread_attrs.tid_core_grp_id_list[ii];
			}
			tid_cnt_for_core_grps[lpgemm_thread_attrs.tid_core_grp_id_list[ii]] += 1;
		}

		for ( int ii = 0; ii < num_core_grps; ++ii )
		{
			if ( adj_tid_cnt_for_core_grps[ii] >= core_grp_loaded_thres )
			{
				core_grp_adj_tid_thres_cnt += 1;
				core_grp_adj_tid_cnt += 1;
			}
			else if ( adj_tid_cnt_for_core_grps[ii] > 0 )
			{
				core_grp_adj_tid_cnt += 1;
			}
			else if( tid_cnt_for_core_grps[ii] > 0)
			{
				core_grp_non_adj_tid_cnt += 1;
			}
		}

		if ( core_grp_adj_tid_cnt > ( 2 * core_grp_non_adj_tid_cnt ) )
		{
			lpgemm_thread_attrs.tid_distr_nearly_seq = TRUE;
		}

		if ( ( core_grp_adj_tid_thres_cnt > 0 ) &&
			 ( core_grp_adj_tid_thres_cnt >=
			   ( core_grp_adj_tid_cnt - core_grp_adj_tid_thres_cnt ) ) )
		{
			lpgemm_thread_attrs.tid_core_grp_load_high = TRUE;
		}
	}

err_handle:
	free( tid_cnt_for_core_grps );
	free( adj_tid_cnt_for_core_grps );

	if (thread_core_bind_list != NULL )
	{
		for ( int ii = 0; ii < nt_max; ++ii )
		{
			free( thread_core_bind_list[ii] );
		}
	}
	free( thread_core_bind_list );
}

#else

static void lpgemm_detect_thread_topo()
{}

#endif // BLIS_ENABLE_OPENMP

void lpgemm_load_thread_attrs()
{
	lpgemm_thread_attrs.tid_core_grp_id_list = NULL;
	lpgemm_thread_attrs.tid_cnt = 0;
	lpgemm_thread_attrs.openmp_enabled = FALSE;
	lpgemm_thread_attrs.tid_distr_nearly_seq = FALSE;
	lpgemm_thread_attrs.tid_core_grp_load_high = FALSE;

	/*
	TODO: Disabling lpgemm_detect_thread_topo detection for now until for 
		  further investigation.
	Reason: libgomp is not honoring standard function omp_get_place_proc_ids
	on virtual machines.
	*/

	// lpgemm_detect_thread_topo();
}

void lpgemm_init_thread_attrs()
{
	bli_pthread_once
	(
	  &once_check_lpgemm_thread_topo_init,
	  lpgemm_load_thread_attrs
	);
}

// Should be called only after aocl_lpgemm_init_global_cntx.
lpgemm_thread_attrs_t* lpgemm_get_thread_attrs()
{
	return &lpgemm_thread_attrs;
}