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/*
* Copyright (C) by Argonne National Laboratory
* See COPYRIGHT in top-level directory
*/
/**
* \file ad_tuning.c
* \brief Defines common performance tuning env var options
*/
/*---------------------------------------------------------------------
* ad_tuning.c
*
* defines common global variables and functions for performance tuning
* and functional debugging.
*---------------------------------------------------------------------*/
#include "ad_tuning.h"
int romio_write_aggmethod;
int romio_read_aggmethod;
int romio_onesided_no_rmw;
int romio_onesided_always_rmw;
int romio_onesided_inform_rmw;
int romio_tunegather;
/* set internal variables for tuning environment variables */
/** \page mpiio_vars MPIIO Configuration
\section env_sec Environment Variables
*
* - ROMIO_WRITE_AGGMETHOD/ROMIO_READ_AGGMETHOD - Replaces the two-phase
* collective IO aggregation
* with a one-sided algorithm, significantly reducing communication and
* memory overhead. Fully
* supports all datasets and datatypes, the only caveat is that any holes in the data
* when writing to a pre-existing file are ignored -- there is no read-modify-write
* support to maintain the correctness of regions of pre-existing data so every byte
* must be explicitly written to maintain correctness. Users must beware of middle-ware
* libraries like PNETCDF which may count on read-modify-write functionality for certain
* features (like fill values). Possible values:
* - 0 - Normal two-phase collective IO is used.
* - 1 - A separate one-sided MPI_Put or MPI_Get is used for each contigous chunk of data
* for a compute to write to or read from the collective buffer on the aggregator.
* - 2 - An MPI derived datatype is created using all the contigous chunks and just one
* call to MPI_Put or MPI_Get is done with the derived datatype. On Blue Gene /Q
* optimal performance for this is achieved when paired with PAMID_TYPED_ONESIDED=1.
* - Default is 0
*
* - ROMIO_ONESIDED_NO_RMW - For one-sided write aggregation (ROMIO_WRITE_AGGMETHOD = 1 or 2)
* disable the detection of holes in the data when writing to a pre-existing
* file requiring a read-modify-write, thereby avoiding the communication
* overhead for this detection.
* - 0 (hole detection enabled) or 1 (hole detection disabled)
* - Default is 0
*
* - ROMIO_ONESIDED_ALWAYS_RMW - For one-sided write aggregation (ROMIO_WRITE_AGGMETHOD = 1 or 2)
* always pre-read the offset range being written to a pre-existing file thereby filling
* any holes that may exist in the data before being written.
* - 0 (do not pre-read file offset range) or 1 (pre-read file offset range)
* - Default is 0
*
* - ROMIO_ONESIDED_INFORM_RMW - For one-sided aggregation
* (ROMIO_WRITE_AGGMETHOD = 1 or 2) generate an informational message informing
* the user whether holes exist in the data when writing to a pre-existing
* file requiring a read-modify-write, thereby educating the user to set
* ROMIO_ONESIDED_NO_RMW=1 on a future run to avoid the communication
* overhead for this detection.
* - 0 (disabled) or 1 (enabled)
* - Default is 0
*
* - ROMIO_TUNEGATHER - Tune how starting and ending offsets are communicated
* for aggregator collective i/o. Possible values:
* - 0 - Use two or three MPI_Allgather's to collect starting and ending offsets.
* - 1 - Use MPI_Allreduce(MPI_MAX) to collect starting and ending offsets.
* - Default is 1.
*
*/
void ad_get_env_vars()
{
char *x;
romio_write_aggmethod = 0;
x = getenv("ROMIO_WRITE_AGGMETHOD");
if (x)
romio_write_aggmethod = atoi(x);
romio_read_aggmethod = 0;
x = getenv("ROMIO_READ_AGGMETHOD");
if (x)
romio_read_aggmethod = atoi(x);
romio_onesided_no_rmw = 0;
x = getenv("ROMIO_ONESIDED_NO_RMW");
if (x)
romio_onesided_no_rmw = atoi(x);
romio_onesided_always_rmw = 0;
x = getenv("ROMIO_ONESIDED_ALWAYS_RMW");
if (x)
romio_onesided_always_rmw = atoi(x);
if (romio_onesided_always_rmw)
romio_onesided_no_rmw = 1;
romio_onesided_inform_rmw = 0;
x = getenv("ROMIO_ONESIDED_INFORM_RMW");
if (x)
romio_onesided_inform_rmw = atoi(x);
romio_tunegather = 1;
x = getenv("ROMIO_TUNEGATHER");
if (x)
romio_tunegather = atoi(x);
}
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