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limit nthr on tiny images 

we always made N threads for a threadpool ... we could end up making
loads of threads we never used if the image was tiny

for very small images, limit the number of threads we make
This commit is contained in:
John Cupitt 2014-07-25 14:51:29 +01:00
parent 91cb6cd8c4
commit 0114afa5fb
3 changed files with 24 additions and 11 deletions
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1
ChangeLog
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@ -1,5 +1,6 @@
25/7/14 started 7.40.5
- fix a race in im_maxpos_avg()
- limit n_thr on tiny images
4/7/14 started 7.40.4
- fix vips_rawsave_fd(), thanks aferrero2707

2
TODO
View File

@ -1,6 +1,4 @@
- threadpool recyling might be useful for dzsave?
- check and fix up docs

32
libvips/iofuncs/threadpool.c
View File

@ -13,6 +13,8 @@
* 17/7/10
* - set pool->error whenever we set thr->error, lets us catch allocate
* errors (thanks Tim)
* 25/7/14
* - limit nthr on tiny images
*/
/*
@ -688,6 +690,10 @@ static VipsThreadpool *
vips_threadpool_new( VipsImage *im )
{
VipsThreadpool *pool;
int tile_width;
int tile_height;
int n_tiles;
int n_lines;
/* Allocate and init new thread block.
*/
@ -705,6 +711,14 @@ vips_threadpool_new( VipsImage *im )
pool->stop = FALSE;
pool->done_first = FALSE;
/* If this is a tiny image, we won't need all nthr threads. Guess how
* many tiles we might need to cover the image and use that to limit
* the number of threads we create.
*/
vips_get_tile_size( im, &tile_width, &tile_height, &n_lines );
n_tiles = (1 + im->Xsize / tile_width) * (1 + im->Ysize / tile_height);
pool->nthr = VIPS_MIN( pool->nthr, n_tiles );
/* Attach tidy-up callback.
*/
g_signal_connect( im, "close",
@ -919,7 +933,7 @@ vips_threadpool_run( VipsImage *im,
* @im: image to guess for
* @tile_width: return selected tile width
* @tile_height: return selected tile height
* @nlines: return buffer height in scanlines
* @n_lines: 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
@ -927,7 +941,7 @@ vips_threadpool_run( VipsImage *im,
*/
void
vips_get_tile_size( VipsImage *im,
int *tile_width, int *tile_height, int *nlines )
int *tile_width, int *tile_height, int *n_lines )
{
const int nthr = vips_concurrency_get();
@ -954,25 +968,25 @@ vips_get_tile_size( VipsImage *im,
g_assert( 0 );
}
/* We can't set nlines for the current demand style: a later bit of
/* 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.
*
* Pick the maximum buffer size we might possibly need, then round up
* to a multiple of tileheight.
*/
*nlines = vips__tile_height *
*n_lines = vips__tile_height *
(1 + nthr / VIPS_MAX( 1, im->Xsize / vips__tile_width )) * 2;
*nlines = VIPS_MAX( *nlines, vips__fatstrip_height * nthr * 2 );
*nlines = VIPS_MAX( *nlines, vips__thinstrip_height * nthr * 2 );
*nlines = ROUND_UP( *nlines, *tile_height );
*n_lines = VIPS_MAX( *n_lines, vips__fatstrip_height * nthr * 2 );
*n_lines = VIPS_MAX( *n_lines, vips__thinstrip_height * nthr * 2 );
*n_lines = ROUND_UP( *n_lines, *tile_height );
/* We make this assumption in several places.
*/
g_assert( *nlines % *tile_height == 0 );
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, *nlines );
*tile_width, *tile_height, *n_lines );
}