libvips/libvips/iofuncs/thread.c

/* Basic functions to support threading.
 * 
 * 29/9/22
 * 	- from threadpool.c
 */

/*

    This file is part of VIPS.
    
    VIPS is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301  USA

 */

/*

    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
#define VIPS_DEBUG
#define VIPS_DEBUG_RED
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /*HAVE_UNISTD_H*/
#include <errno.h>

#include <vips/vips.h>
#include <vips/internal.h>
#include <vips/thread.h>
#include <vips/debug.h>

#ifdef G_OS_WIN32
#include <windows.h>
#endif /*G_OS_WIN32*/

/* Maximum value we allow for VIPS_CONCURRENCY. We need to stop huge values
 * killing the system.
 */
#define MAX_THREADS (1024)

/* Default n threads ... 0 means get from environment.
 */
int vips__concurrency = 0;

/* Default tile geometry ... can be set by vips_init().
 */
int vips__tile_width = VIPS__TILE_WIDTH;
int vips__tile_height = VIPS__TILE_HEIGHT;
int vips__fatstrip_height = VIPS__FATSTRIP_HEIGHT;
int vips__thinstrip_height = VIPS__THINSTRIP_HEIGHT;

/* Set this GPrivate to indicate that is a libvips thread.
 */
static GPrivate *is_vips_thread_key = NULL;

/* TRUE if we are a vips thread. We sometimes manage resource allocation
 * differently for vips threads since we can cheaply free stuff on thread
 * termination.
 */
gboolean
vips_thread_isvips( void )
{
	return( g_private_get( is_vips_thread_key ) != NULL );
}

/* Glib 2.32 revised the thread API. We need some compat functions.
 */

GMutex *
vips_g_mutex_new( void )
{
	GMutex *mutex;

	mutex = g_new( GMutex, 1 );
	g_mutex_init( mutex );

	return( mutex );
}

void
vips_g_mutex_free( GMutex *mutex )
{
	g_mutex_clear( mutex );
	g_free( mutex );
}

GCond *
vips_g_cond_new( void )
{
	GCond *cond;

	cond = g_new( GCond, 1 );
	g_cond_init( cond );

	return( cond );
}

void
vips_g_cond_free( GCond *cond )
{
	g_cond_clear( cond );
	g_free( cond );
}

typedef struct {
	const char *domain; 
	GThreadFunc func; 
	gpointer data;
} VipsThreadInfo; 

static void *
vips_thread_run( gpointer data )
{
	VipsThreadInfo *info = (VipsThreadInfo *) data;

	void *result;

	/* Set this to something (anything) to tag this thread as a vips 
	 * worker. No need to call g_private_replace as there is no
	 * GDestroyNotify handler associated with a worker.
	 */
	g_private_set( is_vips_thread_key, info );

	result = info->func( info->data );

	g_free( info ); 

	vips_thread_shutdown();

	return( result ); 
}

GThread *
vips_g_thread_new( const char *domain, GThreadFunc func, gpointer data )
{
	GThread *thread;
	VipsThreadInfo *info; 
	GError *error = NULL;

	info = g_new( VipsThreadInfo, 1 ); 
	info->domain = domain;
	info->func = func;
	info->data = data;

	thread = g_thread_try_new( domain, vips_thread_run, info, &error );

	VIPS_DEBUG_MSG_RED( "vips_g_thread_new: g_thread_create( %s ) = %p\n",
		domain, thread );

	if( !thread ) {
		if( error ) 
			vips_g_error( &error ); 
		else
			vips_error( domain, 
				"%s", _( "unable to create thread" ) );
	}

	return( thread );
}

static int
get_num_processors( void )
{
#if GLIB_CHECK_VERSION( 2, 48, 1 )
	/* We could use g_get_num_processors when GLib >= 2.48.1, see:
	 * https://gitlab.gnome.org/GNOME/glib/commit/999711abc82ea3a698d05977f9f91c0b73957f7f
	 * https://gitlab.gnome.org/GNOME/glib/commit/2149b29468bb99af3c29d5de61f75aad735082dc
	 */
	return( g_get_num_processors() );
#else
	int nproc;

	nproc = 1;

#ifdef G_OS_UNIX

#if defined(HAVE_UNISTD_H) && defined(_SC_NPROCESSORS_ONLN)
{
	/* POSIX style.
	 */
	int x;

	x = sysconf( _SC_NPROCESSORS_ONLN );
	if( x > 0 )
		nproc = x;
}
#elif defined HW_NCPU
{
	/* BSD style.
	 */
	int x;
	size_t len = sizeof(x);

	sysctl( (int[2]) {CTL_HW, HW_NCPU}, 2, &x, &len, NULL, 0 );
	if( x > 0 )
		nproc = x;
}
#endif

	/* libgomp has some very complex code on Linux to count the number of
	 * processors available to the current process taking pthread affinity
	 * into account, but we don't attempt that here. Perhaps we should?
	 */

#endif /*G_OS_UNIX*/

#ifdef G_OS_WIN32
{
	/* Count the CPUs currently available to this process.  
	 */
	SYSTEM_INFO sysinfo;
	DWORD_PTR process_cpus;
	DWORD_PTR system_cpus;

	/* This *never* fails, use it as fallback 
	 */
	GetNativeSystemInfo( &sysinfo );
	nproc = (int) sysinfo.dwNumberOfProcessors;

	if( GetProcessAffinityMask( GetCurrentProcess(), 
		&process_cpus, &system_cpus ) ) {
		unsigned int af_count;

		for( af_count = 0; process_cpus != 0; process_cpus >>= 1 )
			if( process_cpus & 1 )
				af_count++;

		/* Prefer affinity-based result, if available 
		 */
		if( af_count > 0 )
			nproc = af_count;
	}
}
#endif /*G_OS_WIN32*/

	return( nproc );
#endif /*!GLIB_CHECK_VERSION( 2, 48, 1 )*/
}

/* The default concurrency, set by the environment variable VIPS_CONCURRENCY,
 * or if that is not set, the number of threads available on the host machine.
 */
static int
vips__concurrency_get_default( void )
{
	const char *str;
	int nthr;
	int x;

	/* Tell the threads system how much concurrency we expect.
	 */
	if( vips__concurrency > 0 )
		nthr = vips__concurrency;
	else if( ((str = g_getenv( "VIPS_CONCURRENCY" ))
#if ENABLE_DEPRECATED
		|| (str = g_getenv( "IM_CONCURRENCY" ))
#endif
	) && (x = atoi( str )) > 0 )
		nthr = x;
	else 
		nthr = get_num_processors();

	if( nthr < 1 || 
		nthr > MAX_THREADS ) {
		nthr = VIPS_CLIP( 1, nthr, MAX_THREADS );

		g_warning( _( "threads clipped to %d" ), nthr );
	}

	return( nthr );
}

/**
 * vips_concurrency_set:
 * @concurrency: number of threads to run
 *
 * Sets the number of worker threads that vips should use when running a
 * #VipsThreadPool. 
 *
 * The special value 0 means "default". In this case, the number of threads 
 * is set by the environment variable VIPS_CONCURRENCY, or if that is not 
 * set, the number of threads available on the host machine.
 *
 * See also: vips_concurrency_get().
 */
void
vips_concurrency_set( int concurrency )
{
	/* Tell the threads system how much concurrency we expect.
	 */
	if( concurrency < 1 )
		concurrency = vips__concurrency_get_default();
	else if( concurrency > MAX_THREADS ) {
		concurrency = MAX_THREADS;

		g_warning( _( "threads clipped to %d" ), MAX_THREADS );
	}

	vips__concurrency = concurrency;
}

/**
 * vips_concurrency_get:
 *
 * Returns the number of worker threads that vips should use when running a
 * #VipsThreadPool. 
 *
 * vips gets this values from these sources in turn:
 *
 * If vips_concurrency_set() has been called, this value is used. The special
 * value 0 means "default". You can also use the command-line argument
 * "--vips-concurrency" to set this value.
 *
 * If vips_concurrency_set() has not been called and no command-line argument
 * was used, vips uses the value of the environment variable VIPS_CONCURRENCY,
 *
 * If VIPS_CONCURRENCY has not been set, vips finds the number of hardware
 * threads that the host machine can run in parallel and uses that value. 
 *
 * The final value is clipped to the range 1 - 1024.
 *
 * See also: vips_concurrency_get().
 *
 * Returns: number of worker threads to use.
 */
int
vips_concurrency_get( void )
{
	return( vips__concurrency );
}

/**
 * vips_get_tile_size: (method)
 * @im: image to guess for
 * @tile_width: (out): return selected tile width 
 * @tile_height: (out): return selected tile height 
 * @n_lines: (out): return buffer height in scanlines
 *
 * Pick a tile size and a buffer height for this image and the current
 * value of vips_concurrency_get(). The buffer height 
 * will always be a multiple of tile_height.
 *
 * The buffer height is the height of each buffer we fill in sink disc. Since
 * we have two buffers, the largest range of input locality is twice the output
 * buffer size, plus whatever margin we add for things like convolution. 
 */
void
vips_get_tile_size( VipsImage *im, 
	int *tile_width, int *tile_height, int *n_lines )
{
	const int nthr = vips_concurrency_get();
	const int typical_image_width = 1000;

	/* Compiler warnings.
	 */
	*tile_width = 1;
	*tile_height = 1;

	/* Pick a render geometry.
	 */
	switch( im->dhint ) {
	case VIPS_DEMAND_STYLE_SMALLTILE:
		*tile_width = vips__tile_width;
		*tile_height = vips__tile_height;
		break;

	case VIPS_DEMAND_STYLE_ANY:
	case VIPS_DEMAND_STYLE_FATSTRIP:
		*tile_width = im->Xsize;
		*tile_height = vips__fatstrip_height;
		break;

	case VIPS_DEMAND_STYLE_THINSTRIP:
		*tile_width = im->Xsize;
		/* Only enable thinstrip height for very wide images -- the
		 * overheads are too high to be worthwhile otherwise.
		 */
		*tile_height = im->Xsize > 10000 ? 
			vips__thinstrip_height : vips__fatstrip_height;
		break;

	default:
		g_assert_not_reached();
	}

	/* We can't set n_lines for the current demand style: a later bit of
	 * the pipeline might see a different hint and we need to synchronise
	 * buffer sizes everywhere.
	 *
	 * We also can't depend on the current image size, since that might
	 * change down the pipeline too. Pick a typical image width.
	 *
	 * Pick the maximum buffer size we might possibly need, then round up
	 * to a multiple of tileheight.
	 */
	*n_lines = vips__tile_height * 
		VIPS_ROUND_UP( vips__tile_width * nthr, 
			typical_image_width ) / 
		typical_image_width;
	*n_lines = VIPS_MAX( *n_lines, vips__fatstrip_height * nthr );
	*n_lines = VIPS_MAX( *n_lines, vips__thinstrip_height * nthr );
	*n_lines = VIPS_ROUND_UP( *n_lines, *tile_height );

	/* We make this assumption in several places.
	 */
	g_assert( *n_lines % *tile_height == 0 );

	VIPS_DEBUG_MSG( "vips_get_tile_size: %d by %d patches, "
		"groups of %d scanlines\n", 
		*tile_width, *tile_height, *n_lines );
}

void
vips__thread_init( void )
{
	static GPrivate private = { 0 }; 

	is_vips_thread_key = &private;

	if( vips__concurrency == 0 )
		vips__concurrency = vips__concurrency_get_default();
}