/*
* init_opencl_devices_and_shmem
*
* We can have performance gain using asynchronous DMA transfer when data
* chunk it moved to OpenCL device from host machine, however, it requires
* preparations to ensure the memory region to be copied to/from is pinned
* on RAM; not swapped out. OpenCL provides an interface to map a certain
* host address area as pinned buffer object, even though its size is
* restricted to CL_DEVICE_MAX_MEM_ALLOC_SIZE parameter. Usually, it is
* much less than size of shared memory to be assigned to PG-Strom, around
* 500MB - 2GB in typical GPU/MIC device. So, we need to split a flat
* continuous memory into several 'zones' to pin it using OpenCL interface.
* Because it is a job of OpenCL intermediation server to collect properties
* of devices, and this server shall be launched post initialization stage,
* we also have to acquire and pin the shared memory region in the context
* of OpenCL intermediation server, not postmaster itself.
*/
static void
init_opencl_devices_and_shmem(void)
{
Size zone_length = LONG_MAX;
List *devList;
ListCell *cell;
devList = construct_opencl_device_info(opencl_platform_index);
if (devList == NIL)
elog(ERROR, "PG-Strom: unavailable to use any OpenCL devices");
foreach (cell, devList)
{
pgstrom_device_info *dev_info = lfirst(cell);
if (zone_length > dev_info->dev_max_mem_alloc_size)
zone_length = dev_info->dev_max_mem_alloc_size;
}
/*
* pgstrom_opencl_main
*
* Main routine of opencl intermediation server.
*
* TODO: enhancement to use multi-threaded message handler.
*/
static void
pgstrom_opencl_main(Datum main_arg)
{
pthread_t *threads;
int i;
/* mark this process is OpenCL intermediator */
pgstrom_i_am_clserv = true;
/*
* Set up signal handlers. Currently, OpenCL Server does not pay
* attention on reloading of postgresql.conf, so we can ignore SIGHUP.
*/
pqsignal(SIGHUP, SIG_IGN);
pqsignal(SIGTERM, pgstrom_opencl_sigterm);
/* We're now ready to receive signals */
BackgroundWorkerUnblockSignals();
/* collect opencl platform/device info */
construct_opencl_device_info();
/* initialize opencl context and shared memory segment */
init_opencl_context_and_shmem();
elog(LOG, "Starting PG-Strom OpenCL Server");
/*
* OK, ready to launch server thread. In the default, it creates
* same number with online CPUs, but user can give an explicit
* number using "pg_strom.opencl_num_threads" parameter.
*
* NOTE: sysconf(_SC_NPROCESSORS_ONLN) may not be portable.
*/
if (opencl_num_threads == 0)
opencl_num_threads = sysconf(_SC_NPROCESSORS_ONLN);
Assert(opencl_num_threads > 0);
threads = malloc(sizeof(pthread_t) * opencl_num_threads);
if (!threads)
{
elog(LOG, "out of memory");
return;
}
for (i=0; i < opencl_num_threads; i++)
{
if (pthread_create(&threads[i],
NULL,
pgstrom_opencl_event_loop,
NULL) != 0)
break;
}
/*
* In case of any failure during pthread_create(), worker threads
* will be terminated soon, then we can wait for thread joining.
*/
if (i < opencl_num_threads)
{
elog(LOG, "failed to create server threads");
pgstrom_clserv_exit_pending = true;
pgstrom_cancel_server_loop();
}
else
elog(LOG, "PG-Strom: %d of server threads are up", opencl_num_threads);
while (--i >= 0)
pthread_join(threads[i], NULL);
/* got a signal to stop background worker process */
elog(LOG, "Stopping PG-Strom OpenCL Server");
/*
* close the server queue and returns unprocessed message with error.
*
* XXX - here is possible bug if server got signals during program
* building; that holds some messages and callback enqueues
* the messages again.
*/
pgstrom_close_server_queue();
}
