Merge pull request #1215 from etiennesky/mtr_maxcpus

[FEATURE] add option to set max thread count

src/app/main.cpp

@@ -873,6 +873,10 @@ int main( int argc, char *argv[] )
     mySettings.remove( "/qgis/restoreDefaultWindowState" );
   }
 
+  // set max. thread count
+  // this should be done in QgsApplication::init() but it doesn't know the settings dir.
+  QgsApplication::setMaxThreads( QSettings().value( "/qgis/max_threads", -1 ).toInt() );
+
   QgisApp *qgis = new QgisApp( mypSplash, myRestorePlugins ); // "QgisApp" used to find canonical instance
   qgis->setObjectName( "QgisApp" );
 

src/app/qgsoptions.cpp

@@ -547,6 +547,10 @@ QgsOptions::QgsOptions( QWidget *parent, Qt::WindowFlags fl ) :
   chkUseRenderCaching->setChecked( settings.value( "/qgis/enable_render_caching", false ).toBool() );
   chkParallelRendering->setChecked( settings.value( "/qgis/parallel_rendering", false ).toBool() );
   spinMapUpdateInterval->setValue( settings.value( "/qgis/map_update_interval", 250 ).toInt() );
+  chkMaxThreads->setChecked( QgsApplication::maxThreads() != -1 );
+  spinMaxThreads->setEnabled( chkMaxThreads->isChecked() );
+  spinMaxThreads->setRange( 1, QThread::idealThreadCount() );
+  spinMaxThreads->setValue( QgsApplication::maxThreads() );
 
   // Default simplify drawing configuration
   mSimplifyDrawingGroupBox->setChecked( settings.value( "/qgis/simplifyDrawingHints", ( int )QgsVectorSimplifyMethod::GeometrySimplification ).toInt() != QgsVectorSimplifyMethod::NoSimplification );
@@ -1071,6 +1075,10 @@ void QgsOptions::saveOptions()
   settings.setValue( "/qgis/enable_anti_aliasing", chkAntiAliasing->isChecked() );
   settings.setValue( "/qgis/enable_render_caching", chkUseRenderCaching->isChecked() );
   settings.setValue( "/qgis/parallel_rendering", chkParallelRendering->isChecked() );
+  int maxThreads = chkMaxThreads->isChecked() ? spinMaxThreads->value() : -1;
+  QgsApplication::setMaxThreads( maxThreads );
+  settings.setValue( "/qgis/max_threads", maxThreads );
+
   settings.setValue( "/qgis/map_update_interval", spinMapUpdateInterval->value() );
   settings.setValue( "/qgis/legendDoubleClickAction", cmbLegendDoubleClickAction->currentIndex() );
   bool legendLayersCapitalise = settings.value( "/qgis/capitaliseLayerName", false ).toBool();

src/core/qgsapplication.cpp

@@ -29,6 +29,7 @@
 #include <QSettings>
 #include <QIcon>
 #include <QPixmap>
+#include <QThreadPool>
 
 #ifndef Q_WS_WIN
 #include <netinet/in.h>
@@ -61,6 +62,7 @@ QString ABISYM( QgsApplication::mCfgIntDir );
 #endif
 QString ABISYM( QgsApplication::mBuildOutputPath );
 QStringList ABISYM( QgsApplication::mGdalSkipList );
+int ABISYM( QgsApplication::mMaxThreads );
 
 /*!
   \class QgsApplication
@@ -181,6 +183,11 @@ void QgsApplication::init( QString customConfigPath )
 
   // allow Qt to search for Qt plugins (e.g. sqldrivers) in our plugin directory
   QCoreApplication::addLibraryPath( pluginPath() );
+
+  // set max. thread count to -1
+  // this should be read from QSettings but we don't know where they are at this point
+  // so we read actual value in main.cpp
+  ABISYM( mMaxThreads ) = -1;
 }
 
 QgsApplication::~QgsApplication()
@@ -1016,4 +1023,24 @@ bool QgsApplication::createDB( QString *errorMessage )
   return true;
 }
 
+void QgsApplication::setMaxThreads( int maxThreads )
+{
+  QgsDebugMsg( QString( "maxThreads: %1" ).arg( maxThreads ) );
+
+  // make sure value is between 1 and #cores, if not set to -1 (use #cores)
+  // 0 could be used to disable any parallel processing
+  if ( maxThreads < 1 || maxThreads > QThread::idealThreadCount() )
+    maxThreads = -1;
+
+  // save value
+  ABISYM( mMaxThreads ) = maxThreads;
+
+  // if -1 use #cores
+  if ( maxThreads == -1 )
+    maxThreads = QThread::idealThreadCount();
+
+  // set max thread count in QThreadPool
+  QThreadPool::globalInstance()->setMaxThreadCount( maxThreads );
+  QgsDebugMsg( QString( "set QThreadPool max thread count to %d" ).arg( QThreadPool::globalInstance()->maxThreadCount() ) );
+}
 

src/core/qgsapplication.h

@@ -279,6 +279,14 @@ class CORE_EXPORT QgsApplication : public QApplication
      * @note added in 2.0 */
     static void applyGdalSkippedDrivers();
 
+	/** Get maximum concurrent thread count 
+	 * @note added in 2.4 */
+	static int maxThreads() { return ABISYM( mMaxThreads ); }
+	/** Set maximum concurrent thread count
+	 * @note must be between 1 and #cores, -1 means use all available cores
+	 * @note added in 2.4 */
+	static void setMaxThreads( int maxThreads );
+
 #ifdef ANDROID
     //dummy method to workaround sip generation issue issue
     bool x11EventFilter( XEvent * event )
@@ -320,6 +328,9 @@ class CORE_EXPORT QgsApplication : public QApplication
      * @see skipGdalDriver, restoreGdalDriver
      * @note added in 2.0 */
     static QStringList ABISYM( mGdalSkipList );
+	/** 
+	 * @note added in 2.4 */
+	static int ABISYM( mMaxThreads );
 };
 
 #endif

src/core/qgsmaprendererjob.cpp

@@ -5,6 +5,7 @@
 #include <QTime>
 #include <QTimer>
 #include <QtConcurrentMap>
+#include <QSettings>
 
 #include "qgscrscache.h"
 #include "qgslogger.h"
@@ -731,6 +732,8 @@ void QgsMapRendererParallelJob::start()
 
   mLayerJobs = prepareJobs( 0, mLabelingEngine );
 
+  qDebug( "QThreadPool max thread count is %d", QThreadPool::globalInstance()->maxThreadCount() );
+
   // start async job
 
   connect( &mFutureWatcher, SIGNAL( finished() ), SLOT( renderLayersFinished() ) );

src/ui/qgsoptionsbase.ui

@@ -1629,11 +1629,45 @@
                    </widget>
                   </item>
                   <item>
-                   <widget class="QCheckBox" name="chkParallelRendering">
-                    <property name="text">
-                     <string>Render layers in parallel using all available CPU cores</string>
-                    </property>
-                   </widget>
+                   <layout class="QHBoxLayout" name="horizontalLayout_26">
+                    <item>
+                     <widget class="QCheckBox" name="chkParallelRendering">
+                      <property name="text">
+                       <string>Render layers in parallel using many CPU cores</string>
+                      </property>
+                     </widget>
+                    </item>
+                    <item>
+                     <widget class="Line" name="line_6">
+                      <property name="orientation">
+                       <enum>Qt::Vertical</enum>
+                      </property>
+                     </widget>
+                    </item>
+                    <item>
+                     <widget class="QCheckBox" name="chkMaxThreads">
+                      <property name="text">
+                       <string>Max cores to use:</string>
+                      </property>
+                     </widget>
+                    </item>
+                    <item>
+                     <widget class="QSpinBox" name="spinMaxThreads"/>
+                    </item>
+                    <item>
+                     <spacer name="horizontalSpacer_41">
+                      <property name="orientation">
+                       <enum>Qt::Horizontal</enum>
+                      </property>
+                      <property name="sizeHint" stdset="0">
+                       <size>
+                        <width>40</width>
+                        <height>20</height>
+                       </size>
+                      </property>
+                     </spacer>
+                    </item>
+                   </layout>
                   </item>
                   <item>
                    <layout class="QHBoxLayout" name="horizontalLayout_4">
@@ -4598,5 +4632,21 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>chkMaxThreads</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>spinMaxThreads</receiver>
+   <slot>setEnabled(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>589</x>
+     <y>110</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>689</x>
+     <y>110</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
 </ui>