Производительность эффектов рабочего стола

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Производительность эффектов рабочего стола

Производительность эффектов рабочего стола в KDE Plasma Workspaces в основном определяется взаимодействием аппаратной графики (GPU), это драйвер и Композитор (Kwin). Композитор пытается выбрать наиболее доступные настройки для вашего графического видеоадаптера с определяя помощью запросов драйвера какое оборудование он поддерживает. Иногда помогает KWin улучшить производительность на реально поддерживаемом оборудовании.

Выбор правильного драйвера

Определение используемого драйвера

Очень важно то, что нужный драйвер установлен и используется. Если нет драйвера или используется неправильный драйвер, эффекты рабочего стола вернуться в режим без ускорения (XRender).

Информация об используемом драйвере доступна через KInfoCenter. Щелкните на Сведения о графике -> OpenGL и изучите информацию, представленную в отображенном модуле. Соответствующая информация может быть найдена в разделе Драйвер, в частности в Производитель, Рендерер и Версия OpenGL/ES. Сведения предоставляются драйвером и могут быть трудны для разбора.

Если Renderer говорит: "Software Rasterizer" то это значит, что драйвер не установлен. Для всех других драйверов, пожалуйста, проверьте, правильно ли они используются.

Доступные драйверы

AMD/ATI

Для оборудования AMD/ATI доступны два драйвера: проприетарный fglrx или Catalyst и свободные драйверы Mesa (известные как radeon, r300 и r600). С драйвером fglrx доступна не вся функциональность и общая производительность скорее всего будет лучше при использовании драйверов Mesa. Рекомендуется всегда использовать Mesa драйверы с эффектами рабочего стола. Если вы нашли сведения о "Mesa" в версии OpenGL/ES, то вы используете свободные драйверы и нет необходимости что либо делать.

Mesa драйверы существуют в виде новой и старой версиях. Вы должны убедиться, что используете новые, которые опознаются по слову "Gallium" в строке Renderer.

Intel

Оборудование от Intel использует свободные Mesa драйверы. Нет доступных альтернатив.

NVIDIA

Для оборудования от NVIDIA доступные два драйвера: проприетарный драйвер NVIDIA и свободные Mesa драйверы (известные как nouveau). Свободные драйверы по-прежнему активно разрабатываются и доступны не во всех дистрибутивах и не для всех аппаратных средств. В общем случае рекомендуется использовать проприетарные драйвера. Вы используете проприетарные драйвера в том случае, если в строке Версия OpenGL/ES отображено значение NVIDIA.

Установка драйвера

Installing the driver is specific to the used distribution. Please consult the documentation of your distribution about that matter.

OpenGL Version

KWin supports OpenGL 1.x and OpenGL 2.x. By default KWin uses features of OpenGL 2 if they are available. OpenGL 2 allows to use more effects, but requires stronger hardware. It is important to know that even if your driver only supports e.g. OpenGL 1.4 it is possible that KWin uses features of OpenGL 2 which are available through extensions in the driver.

You can find the OpenGL version provided by your driver in the "OpenGL/ES version" string in KInfoCenter as described above. The version is defined by the first two or three digits, e.g. 2.1.

It is not trivial to find out whether KWin uses OpenGL 1 or 2 as this is completely determined at runtime. The best available test is to use the Invert effect which can be enabled in Systemsettings -> Desktop Effects -> All Effects tab. After enabling the screen should be inverted when using the shortcut Meta + Ctrl + I. If it inverts OpenGL 2 is used, if it does nothing OpenGL 1 is used.

It is possible to force KWin to use OpenGL 1 through Systemsettings -> Desktop Effects -> Advanced tab and unchecking Use OpenGL 2 Shaders. This can improve the performance for older hardware. In general it is completely safe to use OpenGL 2 Shaders if the driver reports a version of 3.x (only available with NVIDIA at the time of this writing).

Tip

For modern hardware the OpenGL 2 Shaders yield a better performance than OpenGL 1. Disabling this option is no receipt for best performance.

kwin_gles

Beginning with KWin version 4.8 it is possible to use the separately built binary kwin_gles as a replacement for kwin. It behaves almost the same as the kwin executable in OpenGL2 mode with the slight difference that it uses egl instead of glx as the native platform interface.

Warning

This also means that if your normal kwin does not work in the OpenGL 2 mode it is unlikely that kwin_gles will.

To test kwin_gles you just have to run kwin_gles --replace in Konsole. Since this is a rather new feature it is not as thoroughly tested as the normal kwin and feedback is always welcome. Assuming that the test succeeded and you want to use kwin_gles on a regular basis you can add an executable script to ~/.kde4/env/ that exports the KDEWM=kwin_gles environment variable.

Thumbnail Scaling

The Compositor supports different scaling methods for thumbnails as rendered in the taskbar preview or effects like Present Windows. It is tried to render the thumbnails as accurate as possible which of course requires more resources.

The scaling method can be changed in Systemsettings -> Desktop Effects -> Advanced tab -> Scale method selection list. The following settings are available:

Crisp
Smooth
Accurate

The table provides an overview of how the thumbnails are rendered with the different settings.

Overview of how the thumbnails are rendered with the different settings
Crisp:
Smooth:
Accurate:

By default Accurate is used. On Intel hardware Accurate is never used and cannot be enabled unless the environment variable KWIN_FORCE_LANCZOS is set to 1.

Switching from Accurate to Smooth can significantly improve the performance of effects like Present Windows.

General Speed of Animations

Animations take some time and the length of an animations is what makes people think that this is a snappy interface or that it lags. This is a very subjective feeling and the difference between too fast and too slow can be milliseconds. It is impossible to have a perfect value for all users.

The global animation duration level can be changed through Systemsettings -> Desktop Effects -> General Tab -> Animation speed selection list. It varies from "Extremely slow" to "Instant" which does not render any animations. By changing from "Normal" to "Fast" many users reported having a more snappy interface.

Qt Graphics System

Since 4.7 (Released July 2011) the Compositor can use the Qt graphics system raster instead of native (X11). This is only relevant for rendering the window decorations and is not related to the compositing backends (OpenGL/XRender).

Which graphics system is used depends on the distribution defaults. For the Compositor raster is recommended especially if the NVIDIA driver is used.

Window Decorations

Some Window Decorations perform animations when a window gets activated. This influences the performance of effects if during an animation the active window changes. The performance impact can be reduced by using the graphics system "raster" (see above).

The default window decoration Oxygen provides an option to disable the animations: Systemsettings -> Workspaces Appearance -> Window Decorations -> Configure Decoration... -> General tab Checkbox Enable animations. Disabling the animations can improve the performance.

All window decorations which can be downloaded through the Get New Decorations... dialog use such animations, but it is not possible to disable them. If there is an performance impact due to the theme, it is recommended to use a different one. In general the themed decorations are not optimized and provided to look good and not to be fast.

Another area of window decorations which can impact the performance are shadows. Again the default decoration Oxygen provides a setting to disable them in the same configuration dialog as described above in tab "Shadows" and the themed decorations do not provide an option to disable shadows.

Blur Effect

The Blur Effect is one of the most expensive effects provided by the Compositor. By default it gets enabled for all hardware except Intel hardware. The performance impact of the blur effect depends on the number of open and translucent windows. Especially translucent widget styles (e.g. Oxygen Translucent) and translucent window decorations (e.g. Aurorae Themes) have an impact on the performance. If such a theme is used and the performance is bad it is recommended to either change the theme or disable the Blur effect.

The performance of the Blur effect can be adjusted through Systemsettings -> Desktop Effects -> All Effects tab -> Configuration dialog of Blur effect. Moving the slider for strength to "Light" requires less resources while moving it towards "Strong" requires more resources. Since 4.8 (release January 2012) the intermediate rendering results can be kept (default) which improves the performance even with translucent themes.

Advanced Desktop Effects Settings

The Compositor provides some advanced settings under Systemsettings -> Desktop Effects -> Advanced tab. Some of the settings have already been explained. This section focuses on the remaining settings. Changing these settings in general do not improve the performance but make it worse. The Compositor uses the best possible settings.

Compositing type

The Compositing type allows choice of the compositing backend, either XRender or OpenGL. By default OpenGL is used which is hardware accelerated. XRender is available even if no OpenGL driver is installed (e.g. virtual machines) and uses mostly the CPU for rendering. Many effects are not available with XRender.

Information

If there is no good reason to change, the default OpenGL is the correct choice. If OpenGL is not available there is an automatic fallback to XRender.

Keep window thumbnails

This has hardly any influence on performance. It is an option to decide how long thumbnails are kept. Best is to not touch this setting.

Suspend desktop effects for fullscreen windows

This setting influences the performance of fullscreen windows such as games. The compositor is suspended as long as there is a fullscreen window. The disadvantage is that it causes flickering when a window appears on top of the fullscreen window (e.g. a context menu) and is too generic. As well on some distributions (e.g. Kubuntu 11.04) the Intel driver causes a crash when closing the fullscreen window.

If the compositor should be disabled while a fullscreen application such as games or video is used it is better to disable compositing either through the shortcut Alt + Shift + F12 or since 4.7 (Released July 2011) through a window specific rule for the window.

OpenGL mode

Warning

The setting is obsolete and has been removed in 4.7 (Released July 2011). Any setting except the default "Texture from Pixmap" is likely to break your desktop.

Enable direct rendering

Warning

The setting is obsolete and has been removed in 4.8 (Released January 2012).

The compositor determines by itself whether direct rendering can and has to be used. Changing this setting will most likely break functionality.

Use VSync

VSync allows you to synchronize the rendering with the screen. Unless there is good reason to change, this setting should be enabled. Even if the setting is disabled the Compositor tries to use the frame rate the screen supports and by default a frame rate of 60 Hz is used.

For multiple screens it is important to know that the rendering can only be synchronized with one screen. In case the screens have a different frame rate it might be valid to disable this option and to set a manual frame rate.