Drop the swap profiler

In hindsight, we want to swap buffers after finishing a compositing
cycle, therefore there is no need for the swap profiler.

platformsupport/scenes/opengl/CMakeLists.txt

@@ -2,7 +2,6 @@ set(SCENE_OPENGL_BACKEND_SRCS
     abstract_egl_backend.cpp
     backend.cpp
     egl_dmabuf.cpp
-    swap_profiler.cpp
     texture.cpp
 )
 

platformsupport/scenes/opengl/swap_profiler.cpp

-/*
-    KWin - the KDE window manager
-    This file is part of the KDE project.
-
-    SPDX-FileCopyrightText: 2006 Lubos Lunak <l.lunak@kde.org>
-    SPDX-FileCopyrightText: 2009, 2010, 2011 Martin Gräßlin <mgraesslin@kde.org>
-
-    SPDX-License-Identifier: GPL-2.0-or-later
-*/
-#include "swap_profiler.h"
-#include <logging.h>
-
-namespace KWin
-{
-
-SwapProfiler::SwapProfiler()
-{
-    init();
-}
-
-void SwapProfiler::init()
-{
-    m_time = 2 * 1000*1000; // we start with a long time mean of 2ms ...
-    m_counter = 0;
-}
-
-void SwapProfiler::begin()
-{
-    m_timer.start();
-}
-
-char SwapProfiler::end()
-{
-    // .. and blend in actual values.
-    // this way we prevent extremes from killing our long time mean
-    m_time = (10*m_time + m_timer.nsecsElapsed())/11;
-    if (++m_counter > 500) {
-        const bool blocks = m_time > 1000 * 1000; // 1ms, i get ~250µs and ~7ms w/o triple buffering...
-        qCDebug(KWIN_OPENGL) << "Triple buffering detection:" << QString(blocks ? QStringLiteral("NOT available") : QStringLiteral("Available")) <<
-                        " - Mean block time:" << m_time/(1000.0*1000.0) << "ms";
-        return blocks ? 'd' : 't';
-    }
-    return 0;
-}
-
-}

platformsupport/scenes/opengl/swap_profiler.h

-/*
-    KWin - the KDE window manager
-    This file is part of the KDE project.
-
-    SPDX-FileCopyrightText: 2006 Lubos Lunak <l.lunak@kde.org>
-    SPDX-FileCopyrightText: 2009, 2010, 2011 Martin Gräßlin <mgraesslin@kde.org>
-
-    SPDX-License-Identifier: GPL-2.0-or-later
-*/
-#ifndef KWIN_SCENE_OPENGL_SWAP_PROFILER_H
-#define KWIN_SCENE_OPENGL_SWAP_PROFILER_H
-
-#include <QElapsedTimer>
-#include <kwin_export.h>
-
-namespace KWin
-{
-
-/**
- * @short Profiler to detect whether we have triple buffering
- * The strategy is to start setBlocksForRetrace(false) but assume blocking and have the system prove that assumption wrong
- */
-class KWIN_EXPORT SwapProfiler
-{
-public:
-    SwapProfiler();
-    void init();
-    void begin();
-    /**
-     * @return char being 'd' for double, 't' for triple (or more - but non-blocking) buffering and
-     * 0 (NOT '0') otherwise, so you can act on "if (char result = SwapProfiler::end()) { fooBar(); }
-     */
-    char end();
-private:
-    QElapsedTimer m_timer;
-    qint64  m_time;
-    int m_counter;
-};
-
-}
-
-#endif

plugins/platforms/x11/common/eglonxbackend.cpp

@@ -62,9 +62,6 @@ EglOnXBackend::EglOnXBackend(xcb_connection_t *connection, Display *display, xcb
     setIsDirectRendering(true);
 }
 
-static bool gs_tripleBufferUndetected = true;
-static bool gs_tripleBufferNeedsDetection = false;
-
 EglOnXBackend::~EglOnXBackend()
 {
     if (isFailed() && m_overlayWindow) {
@@ -72,9 +69,6 @@ EglOnXBackend::~EglOnXBackend()
     }
     cleanup();
 
-    gs_tripleBufferUndetected = true;
-    gs_tripleBufferNeedsDetection = false;
-
     if (m_overlayWindow) {
         if (overlayWindow()->window()) {
             overlayWindow()->destroy();
@@ -118,8 +112,6 @@ void EglOnXBackend::init()
 
     setSyncsToVBlank(false);
     setBlocksForRetrace(false);
-    gs_tripleBufferNeedsDetection = false;
-    m_swapProfiler.init();
     if (surfaceHasSubPost) {
         qCDebug(KWIN_CORE) << "EGL implementation and surface support eglPostSubBufferNV, let's use it";
 
@@ -131,12 +123,6 @@ void EglOnXBackend::init()
                 if (eglSwapInterval(eglDisplay(), 1)) {
                     qCDebug(KWIN_CORE) << "Enabled v-sync";
                     setSyncsToVBlank(true);
-                    const QByteArray tripleBuffer = qgetenv("KWIN_TRIPLE_BUFFER");
-                    if (!tripleBuffer.isEmpty()) {
-                        setBlocksForRetrace(qstrcmp(tripleBuffer, "0") == 0);
-                        gs_tripleBufferUndetected = false;
-                    }
-                    gs_tripleBufferNeedsDetection = gs_tripleBufferUndetected;
                 }
             } else {
                 qCWarning(KWIN_CORE) << "Cannot enable v-sync as max. swap interval is" << val;
@@ -318,32 +304,8 @@ void EglOnXBackend::presentSurface(EGLSurface surface, const QRegion &damage, co
     const bool fullRepaint = supportsBufferAge() || (damage == screenGeometry);
 
     if (fullRepaint || !surfaceHasSubPost) {
-        if (gs_tripleBufferNeedsDetection) {
-            eglWaitGL();
-            m_swapProfiler.begin();
-        }
         // the entire screen changed, or we cannot do partial updates (which implies we enabled surface preservation)
         eglSwapBuffers(eglDisplay(), surface);
-        if (gs_tripleBufferNeedsDetection) {
-            eglWaitGL();
-            if (char result = m_swapProfiler.end()) {
-                gs_tripleBufferUndetected = gs_tripleBufferNeedsDetection = false;
-                if (result == 'd' && GLPlatform::instance()->driver() == Driver_NVidia) {
-                    // TODO this is a workaround, we should get __GL_YIELD set before libGL checks it
-                    if (qstrcmp(qgetenv("__GL_YIELD"), "USLEEP")) {
-                        options->setGlPreferBufferSwap(0);
-                        eglSwapInterval(eglDisplay(), 0);
-                        result = 0; // hint proper behavior
-                        qCWarning(KWIN_CORE) << "\nIt seems you are using the nvidia driver without triple buffering\n"
-                                          "You must export __GL_YIELD=\"USLEEP\" to prevent large CPU overhead on synced swaps\n"
-                                          "Preferably, enable the TripleBuffer Option in the xorg.conf Device\n"
-                                          "For this reason, the tearing prevention has been disabled.\n"
-                                          "See https://bugs.kde.org/show_bug.cgi?id=322060\n";
-                    }
-                }
-                setBlocksForRetrace(result == 'd');
-            }
-        }
         if (supportsBufferAge()) {
             eglQuerySurface(eglDisplay(), surface, EGL_BUFFER_AGE_EXT, &m_bufferAge);
         }
@@ -374,16 +336,6 @@ QRegion EglOnXBackend::beginFrame(int screenId)
 {
     Q_UNUSED(screenId)
     QRegion repaint;
-
-    if (gs_tripleBufferNeedsDetection) {
-        // the composite timer floors the repaint frequency. This can pollute our triple buffering
-        // detection because the glXSwapBuffers call for the new frame has to wait until the pending
-        // one scanned out.
-        // So we compensate for that by waiting an extra milisecond to give the driver the chance to
-        // fllush the buffer queue
-        usleep(1000);
-    }
-
     if (supportsBufferAge())
         repaint = accumulatedDamageHistory(m_bufferAge);
 

plugins/platforms/x11/common/eglonxbackend.h

@@ -9,7 +9,6 @@
 #ifndef KWIN_EGL_ON_X_BACKEND_H
 #define KWIN_EGL_ON_X_BACKEND_H
 #include "abstract_egl_backend.h"
-#include "swap_profiler.h"
 
 #include <xcb/xcb.h>
 
@@ -73,7 +72,6 @@ private:
     xcb_window_t m_renderingWindow = XCB_WINDOW_NONE;
     bool m_havePlatformBase = false;
     bool m_x11TextureFromPixmapSupported = true;
-    SwapProfiler m_swapProfiler;
     friend class EglTexture;
 };
 

plugins/platforms/x11/standalone/glxbackend.cpp

@@ -109,9 +109,6 @@ GlxBackend::GlxBackend(Display *display)
      QOpenGLContext::supportsThreadedOpenGL();
 }
 
-static bool gs_tripleBufferUndetected = true;
-static bool gs_tripleBufferNeedsDetection = false;
-
 GlxBackend::~GlxBackend()
 {
     if (isFailed()) {
@@ -123,9 +120,6 @@ GlxBackend::~GlxBackend()
     doneCurrent();
     EffectQuickView::setShareContext(nullptr);
 
-    gs_tripleBufferUndetected = true;
-    gs_tripleBufferNeedsDetection = false;
-
     if (ctx)
         glXDestroyContext(display(), ctx);
 
@@ -224,19 +218,11 @@ void GlxBackend::init()
     setSyncsToVBlank(false);
     setBlocksForRetrace(false);
     haveWaitSync = false;
-    gs_tripleBufferNeedsDetection = false;
-    m_swapProfiler.init();
     const bool wantSync = options->glPreferBufferSwap() != Options::NoSwapEncourage;
     if (wantSync && glXIsDirect(display(), ctx)) {
         if (haveSwapInterval) { // glXSwapInterval is preferred being more reliable
             setSwapInterval(1);
             setSyncsToVBlank(true);
-            const QByteArray tripleBuffer = qgetenv("KWIN_TRIPLE_BUFFER");
-            if (!tripleBuffer.isEmpty()) {
-                setBlocksForRetrace(qstrcmp(tripleBuffer, "0") == 0);
-                gs_tripleBufferUndetected = false;
-            }
-            gs_tripleBufferNeedsDetection = gs_tripleBufferUndetected;
         } else if (hasExtension(QByteArrayLiteral("GLX_SGI_video_sync"))) {
             unsigned int sync;
             if (glXGetVideoSyncSGI(&sync) == 0 && glXWaitVideoSyncSGI(1, 0, &sync) == 0) {
@@ -719,18 +705,7 @@ void GlxBackend::present(const QRegion &damage)
             Compositor::self()->aboutToSwapBuffers();
 
         if (haveSwapInterval) {
-            if (gs_tripleBufferNeedsDetection) {
-                glXWaitGL();
-                m_swapProfiler.begin();
-            }
             glXSwapBuffers(display(), glxWindow);
-            if (gs_tripleBufferNeedsDetection) {
-                glXWaitGL();
-                if (char result = m_swapProfiler.end()) {
-                    gs_tripleBufferUndetected = gs_tripleBufferNeedsDetection = false;
-                    setBlocksForRetrace(result == 'd');
-                }
-            }
         } else {
             waitSync();
             glXSwapBuffers(display(), glxWindow);
@@ -780,16 +755,6 @@ QRegion GlxBackend::beginFrame(int screenId)
 {
     Q_UNUSED(screenId)
     QRegion repaint;
-
-    if (gs_tripleBufferNeedsDetection) {
-        // the composite timer floors the repaint frequency. This can pollute our triple buffering
-        // detection because the glXSwapBuffers call for the new frame has to wait until the pending
-        // one scanned out.
-        // So we compensate for that by waiting an extra milisecond to give the driver the chance to
-        // fllush the buffer queue
-        usleep(1000);
-    }
-
     makeCurrent();
 
     if (supportsBufferAge())

plugins/platforms/x11/standalone/glxbackend.h

@@ -10,7 +10,6 @@
 #define KWIN_GLX_BACKEND_H
 #include "backend.h"
 #include "texture.h"
-#include "swap_profiler.h"
 #include "x11eventfilter.h"
 
 #include <xcb/glx.h>
@@ -106,7 +105,6 @@ private:
     bool haveSwapInterval = false;
     bool haveWaitSync = false;
     Display *m_x11Display;
-    SwapProfiler m_swapProfiler;
     friend class GlxTexture;
 };