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revise threadpool comments and docs

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This commit is contained in:
John Cupitt 2021-05-11 10:23:05 +01:00
parent e00ca4e6b7
commit eef3f9568d
1 changed files with 38 additions and 28 deletions
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66
libvips/iofuncs/threadpool.c
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@ -56,9 +56,9 @@
*/
/*
*/
#define VIPS_DEBUG
#define VIPS_DEBUG_RED
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
@ -104,8 +104,8 @@
* can be used to give feedback.
*/
/* Maximum number of concurrent threads we allow. No reason for the limit,
* it's just there to stop mad values for VIPS_CONCURRENCY killing the system.
/* Maximum number of concurrent threads we allow. It prevents huge values of
* VIPS_CONCURRENCY killing the system.
*/
#define MAX_THREADS (1024)
@ -120,7 +120,8 @@ int vips__thinstrip_height = VIPS__THINSTRIP_HEIGHT;
*/
int vips__concurrency = 0;
/* Set this GPrivate to indicate that this is a vips worker.
/* Set this GPrivate to indicate that this thread is a worker inside
* the vips threadpool.
*/
static GPrivate *is_worker_key = NULL;
@ -213,6 +214,9 @@ vips_thread_main_loop( gpointer thread_data, gpointer pool_data )
g_free( exec );
/* Free all thread-private caches, since they probably won't be valid
* for the next task this thread is given.
*/
vips_thread_shutdown();
}
@ -318,13 +322,14 @@ vips__concurrency_get_default( void )
else
nthr = get_num_processors();
if( nthr < 1 || nthr > MAX_THREADS ) {
if( nthr < 1 ||
nthr > MAX_THREADS ) {
nthr = VIPS_CLIP( 1, nthr, MAX_THREADS );
g_warning( _( "threads clipped to %d" ), nthr );
}
return nthr;
return( nthr );
}
/**
@ -371,7 +376,7 @@ vips_concurrency_set( int concurrency )
* 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 find the number of hardware
* 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.
@ -386,6 +391,10 @@ vips_concurrency_get( void )
return( vips__concurrency );
}
/* The VipsThreadStartFn arg to vips_threadpool_run() is called once for each
* thread to make one of these things to hold the thread state.
*/
G_DEFINE_TYPE( VipsThreadState, vips_thread_state, VIPS_TYPE_OBJECT );
static void
@ -441,7 +450,7 @@ vips_thread_state_set( VipsObject *object, void *a, void *b )
VipsThreadState *state = (VipsThreadState *) object;
VipsImage *im = (VipsImage *) a;
VIPS_DEBUG_MSG( "vips_thread_state_set:\n" );
VIPS_DEBUG_MSG( "vips_thread_state_set: image %p\n", im );
state->im = im;
state->a = b;
@ -452,13 +461,13 @@ vips_thread_state_set( VipsObject *object, void *a, void *b )
VipsThreadState *
vips_thread_state_new( VipsImage *im, void *a )
{
VIPS_DEBUG_MSG( "vips_thread_state_new:\n" );
VIPS_DEBUG_MSG( "vips_thread_state_new: image %p\n", im );
return( VIPS_THREAD_STATE( vips_object_new(
VIPS_TYPE_THREAD_STATE, vips_thread_state_set, im, a ) ) );
}
/* What we track for a task within the #VipsThreadPool.
/* A VipsTask is the state of one call to vips_threadpool_run().
*/
typedef struct _VipsTask {
/* All private.
@ -493,8 +502,7 @@ typedef struct _VipsTask {
gboolean stop;
} VipsTask;
/* Run this once per main loop. Get some work (single-threaded), then do it
* (many-threaded).
/* Allocate some work (single-threaded), then do it (many-threaded).
*
* The very first workunit is also executed single-threaded. This gives
* loaders a change to seek to the correct spot, see vips_sequential().
@ -511,7 +519,7 @@ vips_task_work_unit( VipsTask *task, VipsThreadState *state )
VIPS_GATE_STOP( "vips_task_work_unit: wait" );
/* Has another worker signaled stop while we've been working?
/* Has another worker signaled stop while we've been waiting?
*/
if( task->stop ) {
g_mutex_unlock( task->allocate_lock );
@ -550,7 +558,7 @@ vips_task_work_unit( VipsTask *task, VipsThreadState *state )
task->error = TRUE;
}
/* What runs as a thread ... loop, waiting to be told to do stuff.
/* What runs as a pipeline thread ... loop, waiting to be told to do stuff.
*/
static void
vips_task_run( gpointer data, gpointer user_data )
@ -594,7 +602,8 @@ vips__threadpool_shutdown( void )
/* We may come here without having inited.
*/
if( vips__pool ) {
VIPS_DEBUG_MSG( "vips__threadpool_shutdown: (%p)\n", vips__pool );
VIPS_DEBUG_MSG( "vips__threadpool_shutdown: (%p)\n",
vips__pool );
g_thread_pool_free( vips__pool, TRUE, TRUE );
vips__pool = NULL;
@ -610,8 +619,6 @@ vips_task_new( VipsImage *im, int *n_tasks )
gint64 n_tiles;
int n_lines;
/* Allocate and init a new task.
*/
if( !(task = VIPS_NEW( NULL, VipsTask )) )
return( NULL );
task->im = im;
@ -632,7 +639,7 @@ vips_task_new( VipsImage *im, int *n_tasks )
vips_get_tile_size( im, &tile_width, &tile_height, &n_lines );
n_tiles = (1 + (gint64) im->Xsize / tile_width) *
(1 + (gint64) im->Ysize / tile_height);
n_tiles = VIPS_MAX( 0, n_tiles );
n_tiles = VIPS_MAX( 1, n_tiles );
*n_tasks = VIPS_MIN( *n_tasks, n_tiles );
VIPS_DEBUG_MSG( "vips_task_new: \"%s\" (%p), with %d tasks\n",
@ -654,21 +661,15 @@ vips_task_free( VipsTask *task )
}
/**
* vips_threadpool_push.
* vips_threadpool_push:
* @name an name for the thread
* @func a function to execute in the thread pool
* @data an argument to supply to @func
*
* Inserts a new function into the list of tasks to be executed by the
* Add a new function to the list of tasks to be executed by the
* #VipsThreadPool. A newly created or reused thread will execute
* @func with with the argument data.
*
* When the number of currently running threads is lower than the
* maximal allowed number of threads set by vips_concurrency_set(),
* a new thread is started (or reused).
* Otherwise, it stays in the queue until a thread in this pool
* finishes its previous task and processes the @func.
*
* See also: vips_concurrency_set().
*
* Returns: 0 on success, -1 on error.
@ -691,6 +692,9 @@ vips_threadpool_push( const char *name, GFunc func, gpointer data )
return( -1 );
}
VIPS_DEBUG_MSG( "vips_threadpool_push: %u threads in pool\n",
g_thread_pool_get_num_threads( vips__pool ) );
return( result ? 0 : -1 );
}
@ -818,7 +822,7 @@ vips_threadpool_run( VipsImage *im,
task->work = work;
task->a = a;
/* Put the tasks to work.
/* Create a set of workers for this pipeline.
*/
for( i = 0; i < n_tasks; i++ )
if( vips_threadpool_push( "worker", vips_task_run, task ) )
@ -859,7 +863,7 @@ vips_threadpool_run( VipsImage *im,
return( result );
}
/* Create a new threadpool. This is called during vips_init.
/* Create the vips threadpool. This is called during vips_init.
*/
void
vips__threadpool_init( void )
@ -874,8 +878,14 @@ vips__threadpool_init( void )
if( vips__concurrency == 0 )
vips__concurrency = vips__concurrency_get_default();
/* We can have many more than vips__concurrency threads -- each active
* pipeline will make vips__concurrency more, see
* vips_threadpool_run().
*/
vips__pool = g_thread_pool_new( vips_thread_main_loop, NULL,
-1, FALSE, NULL );
VIPS_DEBUG_MSG( "vips__threadpool_init: (%p)\n", vips__pool );
}
/**