From fb0af62d0f6e211bdb979f2084d589dc2391bc2b Mon Sep 17 00:00:00 2001
From: Cristy <urban-warrior@imagemagick.org>
Date: Tue, 2 Jan 2024 12:29:58 -0500
Subject: [PATCH] thread tuning

---
 magick/resize.c         |  2 +-
 magick/resource.c       | 10 ++++++----
 magick/thread-private.h | 15 ++++++---------
 3 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/magick/resize.c b/magick/resize.c
index 2ebfefd75..d4aeef962 100644
--- a/magick/resize.c
+++ b/magick/resize.c
@@ -3149,7 +3149,7 @@ MagickExport Image *SampleImage(const Image *image,const size_t columns,
   sample_view=AcquireAuthenticCacheView(sample_image,exception);
 #if defined(MAGICKCORE_OPENMP_SUPPORT)
   #pragma omp parallel for schedule(static) shared(status) \
-    magick_number_threads(image,sample_image,sample_image->rows,1)
+    magick_number_threads(image,sample_image,sample_image->rows,2)
 #endif
   for (y=0; y < (ssize_t) sample_image->rows; y++)
   {
diff --git a/magick/resource.c b/magick/resource.c
index df2a330b2..6dd009b25 100644
--- a/magick/resource.c
+++ b/magick/resource.c
@@ -1401,11 +1401,10 @@ MagickExport MagickBooleanType ResourceComponentGenesis(void)
   MagickSizeType
     memory;
 
-  ssize_t
-    i;
-
   ssize_t
     files,
+    i,
+    number_threads,
     pages,
     pagesize;
 
@@ -1502,7 +1501,10 @@ MagickExport MagickBooleanType ResourceComponentGenesis(void)
       (void) SetMagickResourceLimit(FileResource,StringToSizeType(limit,100.0));
       limit=DestroyString(limit);
     }
-  (void) SetMagickResourceLimit(ThreadResource,GetOpenMPMaximumThreads());
+  number_threads=(ssize_t) GetOpenMPMaximumThreads();
+  if (number_threads > 1)
+    number_threads--;  /* reserve core for OS */
+  (void) SetMagickResourceLimit(ThreadResource,(size_t) number_threads);
   limit=GetEnvironmentValue("MAGICK_THREAD_LIMIT");
   if (limit != (char *) NULL)
     {
diff --git a/magick/thread-private.h b/magick/thread-private.h
index 2715da71e..f9cc6849d 100644
--- a/magick/thread-private.h
+++ b/magick/thread-private.h
@@ -50,7 +50,7 @@ extern "C" {
 static inline int GetMagickNumberThreads(const Image *source,
   const Image *destination,const size_t chunk,int factor)
 {
-#define WorkloadFactor  (32 << factor)
+#define WorkLoadFactor  (64UL << factor)
 
   const CacheType
     destination_type = (CacheType) GetImagePixelCacheType(destination),
@@ -62,15 +62,12 @@ static inline int GetMagickNumberThreads(const Image *source,
   /*
     Return number of threads dependent on cache type and work load.
   */
-  if (factor == 0)
-    return(1);
+  number_threads=MagickMax(MagickMin(chunk/WorkLoadFactor,
+    GetMagickResourceLimit(ThreadResource)),1);
   if (((source_type != MemoryCache) && (source_type != MapCache)) ||
       ((destination_type != MemoryCache) && (destination_type != MapCache)))
-    number_threads=(int) MagickMin(GetMagickResourceLimit(ThreadResource),2);
-  else
-    number_threads=(int) MagickMin((ssize_t) GetMagickResourceLimit(
-      ThreadResource),(ssize_t) (chunk)/WorkloadFactor);
-  return(MagickMax(number_threads,1));
+    number_threads=MagickMin(number_threads,2);
+  return(number_threads);
 }
 
 static inline MagickThreadType GetMagickThreadId(void)
@@ -161,7 +158,7 @@ static inline void SetOpenMPNested(const int value)
   omp_set_nested(value);
 #else
 static inline void SetOpenMPNested(const int magick_unused(value))
-{  
+{
   magick_unreferenced(value);
 #endif
 }