[babl] babl: change MAX_BUFFER_SIZE to 512

[Øyvind Kolås <ok src gnome org>]

commit f2bf5d4f1160617abfd2c76ba10bc4e19b8f0205
Author: Øyvind Kolås <pippin gimp org>
Date:   Fri Sep 1 00:02:32 2017 +0200

    babl: change MAX_BUFFER_SIZE to 512
    
    This is the value that determins the smaller size big buffers are broken up in
    and processed chunk-by chunk for multi-path conversions.
    
    With tools/babl-benchmark for a particular workload and machine the following
    results were attained, all values are in mb/s. There seem to be two sweet-spots
    one around 128 and one around 512. Now using 512 which probably has better
    cache behavior on most cpus than the old value 2048.
    
    MAX_BUFFER_SIZE benchmarks,
        8:  437.1
       16:  458.8
       32:  495.0
       64:  482.6
       96:  496.4
      127:  508.8
      128:  514.2 506.7 495.1
      130:  494.6
      150:  479.5
      255:  492.2
      256:  491.0 486.8
      384:  500.8
      450:  503.7
      500:  499.6 496.5
      511:  477.8
      512:  511.0 508.7 500.6
      514:  499.3
      515:  504.7 502
      520:  512.9 491
      530:  501.8
      550:  483.3
      768:  493.0
     1024:  491.6
     2048:  489.5
     4096:  501.2
     8192:  499.0

 babl/babl-fish-path.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/babl/babl-fish-path.c b/babl/babl-fish-path.c
index 1dd8516..202778a 100644
--- a/babl/babl-fish-path.c
+++ b/babl/babl-fish-path.c
@@ -31,7 +31,7 @@
 #endif
 
 #define NUM_TEST_PIXELS            (babl_get_num_path_test_pixels ())
-#define MAX_BUFFER_SIZE            2048 /* XXX: reasonable size for this should be profiled */
+#define MAX_BUFFER_SIZE            512
 
 
 int   babl_in_fish_path = 0;