The Mesa 3D Graphics Library

# Environment Variables

Normally, no environment variables need to be set. Most of the environment variables used by Mesa/Gallium are for debugging purposes, but they can sometimes be useful for debugging end-user issues.

## LibGL environment variables

`LIBGL_DEBUG`
  If defined debug information will be printed to stderr. If set to `verbose` additional information will be printed.
`LIBGL_DRIVERS_PATH`
  colon-separated list of paths to search for DRI drivers
`LIBGL_ALWAYS_INDIRECT`
  if set to `true`, forces an indirect rendering context/connection.
`LIBGL_ALWAYS_SOFTWARE`
  if set to `true`, always use software rendering
`LIBGL_NO_DRAWARRAYS`
  if set to `true`, do not use DrawArrays GLX protocol (for debugging)
`LIBGL_SHOW_FPS`
  print framerate to stdout based on the number of `glXSwapBuffers` calls per second.
`LIBGL_DRI3_DISABLE`
  disable DRI3 if set to `true`.

## Core Mesa environment variables

`MESA_NO_ASM`
  if set, disables all assembly language optimizations
`MESA_NO_MMX`
  if set, disables Intel MMX optimizations
`MESA_NO_3DNOW`
  if set, disables AMD 3DNow! optimizations
`MESA_NO_SSE`
  if set, disables Intel SSE optimizations
`MESA_NO_ERROR`
  if set to 1, error checking is disabled as per `KHR_no_error`. This will result in undefined behaviour for invalid use of the api, but can reduce CPU use for apps that are known to be error free.
`MESA_DEBUG`
  if set, error messages are printed to stderr. For example, if the application generates a `GL_INVALID_ENUM` error, a corresponding error message indicating where the error occurred, and possibly why, will be printed to stderr. For release builds, `MESA_DEBUG` defaults to off (no debug output). `MESA_DEBUG` accepts the following comma-separated list of named flags, which adds extra behaviour to just set `MESA_DEBUG=1`:
  `silent`
    turn off debug messages. Only useful for debug builds.
  `flush`
    flush after each drawing command
  `incomplete_tex`
    extra debug messages when a texture is incomplete
  `incomplete_fbo`
    extra debug messages when a fbo is incomplete
  `context`
    create a debug context (see `GLX_CONTEXT_DEBUG_BIT_ARB`) and print error and performance messages to stderr (or `MESA_LOG_FILE`).
`MESA_LOG_FILE`
  specifies a file name for logging all errors, warnings, etc., rather than stderr
`MESA_TEX_PROG`
  if set, implement conventional texture env modes with fragment programs (intended for developers only)
`MESA_TNL_PROG`
  if set, implement conventional vertex transformation operations with vertex programs (intended for developers only). Setting this variable automatically sets the `MESA_TEX_PROG` variable as well.
`MESA_EXTENSION_OVERRIDE`
  can be used to enable/disable extensions. A value such as `GL_EXT_foo -GL_EXT_bar` will enable the `GL_EXT_foo` extension and disable the `GL_EXT_bar` extension.
`MESA_EXTENSION_MAX_YEAR`
  The `GL_EXTENSIONS` string returned by Mesa is sorted by extension year. If this variable is set to year X, only extensions defined on or before year X will be reported. This is to work-around a bug in some games where the extension string is copied into a fixed-size buffer without truncating. If the extension string is too long, the buffer overrun can cause the game to crash. This is a work-around for that.
`MESA_GL_VERSION_OVERRIDE`
  changes the value returned by `glGetString(GL_VERSION)` and possibly the GL API type.
  - The format should be `MAJOR.MINOR[FC|COMPAT]`
  - `FC` is an optional suffix that indicates a forward compatible context. This is only valid for versions >= 3.0.
  - `COMPAT` is an optional suffix that indicates a compatibility context or `GL_ARB_compatibility` support. This is only valid for versions >= 3.1.
  - GL versions <= 3.0 are set to a compatibility (non-Core) profile
  - GL versions = 3.1, depending on the driver, it may or may not have the `ARB_compatibility` extension enabled.
  - GL versions >= 3.2 are set to a Core profile
  - Examples:
    `2.1`
      select a compatibility (non-Core) profile with GL version 2.1.
    `3.0`
      select a compatibility (non-Core) profile with GL version 3.0.
    `3.0FC`
      select a Core+Forward Compatible profile with GL version 3.0.
    `3.1`
      select GL version 3.1 with `GL_ARB_compatibility` enabled per the driver default.
    `3.1FC`
      select GL version 3.1 with forward compatibility and `GL_ARB_compatibility` disabled.
    `3.1COMPAT`
      select GL version 3.1 with `GL_ARB_compatibility` enabled.
    `X.Y`
      override GL version to X.Y without changing the profile.
    `X.YFC`
      select a Core+Forward Compatible profile with GL version X.Y.
    `X.YCOMPAT`
      select a Compatibility profile with GL version X.Y.
  - Mesa may not really implement all the features of the given version. (for developers only)
`MESA_GLES_VERSION_OVERRIDE`
  changes the value returned by `glGetString(GL_VERSION)` for OpenGL ES.
  - The format should be `MAJOR.MINOR`
  - Examples: `2.0`, `3.0`, `3.1`
  - Mesa may not really implement all the features of the given version. (for developers only)
`MESA_GLSL_VERSION_OVERRIDE`
  changes the value returned by `glGetString(GL_SHADING_LANGUAGE_VERSION)`. Valid values are integers, such as `130`. Mesa will not really implement all the features of the given language version if it's higher than what's normally reported. (for developers only)
`MESA_GLSL_CACHE_DISABLE`
  if set to `true`, disables the GLSL shader cache
`MESA_GLSL_CACHE_MAX_SIZE`
  if set, determines the maximum size of the on-disk cache of compiled GLSL programs. Should be set to a number optionally followed by `K`, `M`, or `G` to specify a size in kilobytes, megabytes, or gigabytes. By default, gigabytes will be assumed. And if unset, a maximum size of 1GB will be used. Note: A separate cache might be created for each architecture that Mesa is installed for on your system. For example under the default settings you may end up with a 1GB cache for x86_64 and another 1GB cache for i386.
`MESA_GLSL_CACHE_DIR`
  if set, determines the directory to be used for the on-disk cache of compiled GLSL programs. If this variable is not set, then the cache will be stored in `$XDG_CACHE_HOME/mesa_shader_cache` (if that variable is set), or else within `.cache/mesa_shader_cache` within the user's home directory.
`MESA_GLSL`
  shading language compiler options
`MESA_NO_MINMAX_CACHE`
  when set, the minmax index cache is globally disabled.
`MESA_SHADER_CAPTURE_PATH`
  see Capturing Shaders
`MESA_SHADER_DUMP_PATH` and `MESA_SHADER_READ_PATH`
  see Experimenting with Shader Replacements
`MESA_VK_VERSION_OVERRIDE`
  changes the Vulkan physical device version as returned in `VkPhysicalDeviceProperties::apiVersion`.
  - The format should be `MAJOR.MINOR[.PATCH]`
  - This will not let you force a version higher than the driver's instance version as advertised by `vkEnumerateInstanceVersion`
  - This can be very useful for debugging but some features may not be implemented correctly. (For developers only)

## NIR passes enviroment variables

The following are only applicable for drivers that uses NIR, as they modify the behaviour for the common NIR_PASS and NIR_PASS_V macros, that wrap calls to NIR lowering/optimizations.

`NIR_PRINT`
  If defined, the resulting NIR shader will be printed out at each succesful NIR lowering/optimization call.
`NIR_TEST_CLONE`
  If defined, cloning a NIR shader would be tested at each succesful NIR lowering/optimization call.
`NIR_TEST_SERIALIZE`
  If defined, serialize and deserialize a NIR shader would be tested at each succesful NIR lowering/optimization call.

## Mesa Xlib driver environment variables

The following are only applicable to the Mesa Xlib software driver. See the Xlib software driver page for details.

`MESA_RGB_VISUAL`
  specifies the X visual and depth for RGB mode
`MESA_CI_VISUAL`
  specifies the X visual and depth for CI mode
`MESA_BACK_BUFFER`
  specifies how to implement the back color buffer, either `pixmap` or `ximage`
`MESA_GAMMA`
  gamma correction coefficients for red, green, blue channels
`MESA_XSYNC`
  enable synchronous X behavior (for debugging only)
`MESA_GLX_FORCE_CI`
  if set, force GLX to treat 8bpp visuals as CI visuals
`MESA_GLX_FORCE_ALPHA`
  if set, forces RGB windows to have an alpha channel.
`MESA_GLX_DEPTH_BITS`
  specifies default number of bits for depth buffer.
`MESA_GLX_ALPHA_BITS`
  specifies default number of bits for alpha channel.

## i945/i965 driver environment variables (non-Gallium)

`INTEL_NO_HW`
  if set to 1, prevents batches from being submitted to the hardware. This is useful for debugging hangs, etc.
`INTEL_DEBUG`
  a comma-separated list of named flags, which do various things:
  `ann`
    annotate IR in assembly dumps
  `aub`
    dump batches into an AUB trace for use with simulation tools
  `bat`
    emit batch information
  `blit`
    emit messages about blit operations
  `blorp`
    emit messages about the blorp operations (blits & clears)
  `buf`
    emit messages about buffer objects
  `clip`
    emit messages about the clip unit (for old gens, includes the CLIP program)
  `color`
    use color in output
  `cs`
    dump shader assembly for compute shaders
  `do32`
    generate compute shader SIMD32 programs even if workgroup size doesn't exceed the SIMD16 limit
  `dri`
    emit messages about the DRI interface
  `fbo`
    emit messages about framebuffers
  `fs`
    dump shader assembly for fragment shaders
  `gs`
    dump shader assembly for geometry shaders
  `hex`
    print instruction hex dump with the disassembly
  `l3`
    emit messages about the new L3 state during transitions
  `miptree`
    emit messages about miptrees
  `no8`
    don't generate SIMD8 fragment shader
  `no16`
    suppress generation of 16-wide fragment shaders. useful for debugging broken shaders
  `nocompact`
    disable instruction compaction
  `nodualobj`
    suppress generation of dual-object geometry shader code
  `nofc`
    disable fast clears
  `norbc`
    disable single sampled render buffer compression
  `optimizer`
    dump shader assembly to files at each optimization pass and iteration that make progress
  `perf`
    emit messages about performance issues
  `perfmon`
    emit messages about `AMD_performance_monitor`
  `pix`
    emit messages about pixel operations
  `prim`
    emit messages about drawing primitives
  `reemit`
    mark all state dirty on each draw call
  `sf`
    emit messages about the strips & fans unit (for old gens, includes the SF program)
  `shader_time`
    record how much GPU time is spent in each shader
  `spill_fs`
    force spilling of all registers in the scalar backend (useful to debug spilling code)
  `spill_vec4`
    force spilling of all registers in the vec4 backend (useful to debug spilling code)
  `state`
    emit messages about state flag tracking
  `submit`
    emit batchbuffer usage statistics
  `sync`
    after sending each batch, emit a message and wait for that batch to finish rendering
  `tcs`
    dump shader assembly for tessellation control shaders
  `tes`
    dump shader assembly for tessellation evaluation shaders
  `tex`
    emit messages about textures.
  `urb`
    emit messages about URB setup
  `vert`
    emit messages about vertex assembly
  `vs`
    dump shader assembly for vertex shaders
`INTEL_SCALAR_VS` (or `TCS`, `TES`, `GS`)
  force scalar/vec4 mode for a shader stage (Gen8-9 only)
`INTEL_PRECISE_TRIG`
  if set to 1, true or yes, then the driver prefers accuracy over performance in trig functions.

## Radeon driver environment variables (radeon, r200, and r300g)

`RADEON_NO_TCL`
  if set, disable hardware-accelerated Transform/Clip/Lighting.

## EGL environment variables

Mesa EGL supports different sets of environment variables. See the Mesa EGL page for the details.

## Gallium environment variables

`GALLIUM_HUD`
  draws various information on the screen, like framerate, cpu load, driver statistics, performance counters, etc. Set `GALLIUM_HUD=help` and run e.g. `glxgears` for more info.
`GALLIUM_HUD_PERIOD`
  sets the hud update rate in seconds (float). Use zero to update every frame. The default period is 1/2 second.
`GALLIUM_HUD_VISIBLE`
  control default visibility, defaults to true.
`GALLIUM_HUD_TOGGLE_SIGNAL`
  toggle visibility via user specified signal. Especially useful to toggle hud at specific points of application and disable for unencumbered viewing the rest of the time. For example, set `GALLIUM_HUD_VISIBLE` to `false` and `GALLIUM_HUD_TOGGLE_SIGNAL` to `10` (`SIGUSR1`). Use `kill -10 <pid>` to toggle the hud as desired.
`GALLIUM_HUD_DUMP_DIR`
  specifies a directory for writing the displayed hud values into files.
`GALLIUM_DRIVER`
  useful in combination with `LIBGL_ALWAYS_SOFTWARE=true` for choosing one of the software renderers `softpipe`, `llvmpipe` or `swr`.
`GALLIUM_LOG_FILE`
  specifies a file for logging all errors, warnings, etc. rather than stderr.
`GALLIUM_PRINT_OPTIONS`
  if non-zero, print all the Gallium environment variables which are used, and their current values.
`GALLIUM_DUMP_CPU`
  if non-zero, print information about the CPU on start-up
`TGSI_PRINT_SANITY`
  if set, do extra sanity checking on TGSI shaders and print any errors to stderr.
`DRAW_FSE`
  ???
`DRAW_NO_FSE`
  ???
`DRAW_USE_LLVM`
  if set to zero, the draw module will not use LLVM to execute shaders, vertex fetch, etc.
`ST_DEBUG`
  controls debug output from the Mesa/Gallium state tracker. Setting to `tgsi`, for example, will print all the TGSI shaders. See `src/mesa/state_tracker/st_debug.c` for other options.

### Clover state tracker environment variables

`CLOVER_EXTRA_BUILD_OPTIONS`
  allows specifying additional compiler and linker options. Specified options are appended after the options set by the OpenCL program in `clBuildProgram`.
`CLOVER_EXTRA_COMPILE_OPTIONS`
  allows specifying additional compiler options. Specified options are appended after the options set by the OpenCL program in `clCompileProgram`.
`CLOVER_EXTRA_LINK_OPTIONS`
  allows specifying additional linker options. Specified options are appended after the options set by the OpenCL program in `clLinkProgram`.

### Softpipe driver environment variables

`SOFTPIPE_DUMP_FS`
  if set, the softpipe driver will print fragment shaders to stderr
`SOFTPIPE_DUMP_GS`
  if set, the softpipe driver will print geometry shaders to stderr
`SOFTPIPE_NO_RAST`
  if set, rasterization is no-op'd. For profiling purposes.
`SOFTPIPE_USE_LLVM`
  if set, the softpipe driver will try to use LLVM JIT for vertex shading processing.

### LLVMpipe driver environment variables

`LP_NO_RAST`
  if set LLVMpipe will no-op rasterization
`LP_DEBUG`
  a comma-separated list of debug options is accepted. See the source code for details.
`LP_PERF`
  a comma-separated list of options to selectively no-op various parts of the driver. See the source code for details.
`LP_NUM_THREADS`
  an integer indicating how many threads to use for rendering. Zero turns off threading completely. The default value is the number of CPU cores present.

### VMware SVGA driver environment variables

`SVGA_FORCE_SWTNL`
  force use of software vertex transformation
`SVGA_NO_SWTNL`
  don't allow software vertex transformation fallbacks (will often result in incorrect rendering).
`SVGA_DEBUG`
  for dumping shaders, constant buffers, etc. See the code for details.
`SVGA_EXTRA_LOGGING`
  if set, enables extra logging to the `vmware.log` file, such as the OpenGL program's name and command line arguments.
`SVGA_NO_LOGGING`
  if set, disables logging to the `vmware.log` file. This is useful when using Valgrind because it otherwise crashes when initializing the host log feature.

See the driver code for other, lesser-used variables.

### WGL environment variables

`WGL_SWAP_INTERVAL`
  to set a swap interval, equivalent to calling `wglSwapIntervalEXT()` in an application. If this environment variable is set, application calls to `wglSwapIntervalEXT()` will have no effect.

### VA-API state tracker environment variables

`VAAPI_MPEG4_ENABLED`
  enable MPEG4 for VA-API, disabled by default.

### VC4 driver environment variables

`VC4_DEBUG`
  a comma-separated list of named flags, which do various things:
  `cl`
    dump command list during creation
  `qpu`
    dump generated QPU instructions
  `qir`
    dump QPU IR during program compile
  `nir`
    dump NIR during program compile
  `tgsi`
    dump TGSI during program compile
  `shaderdb`
    dump program compile information for shader-db analysis
  `perf`
    print during performance-related events
  `norast`
    skip actual hardware execution of commands
  `always_flush`
    flush after each draw call
  `always_sync`
    wait for finish after each flush
  `dump`
    write a GPU command stream trace file (VC4 simulator only)

Other Gallium drivers have their own environment variables. These may change frequently so the source code should be consulted for details.