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]
  • FC is an optional suffix that indicates a forward compatible context. This is only valid for versions >= 3.0.
  • GL versions < 3.0 are set to a compatibility (non-Core) profile
  • GL versions = 3.0, see below
  • GL versions > 3.0 are set to a Core profile
  • Examples: 2.1, 3.0, 3.0FC, 3.1, 3.1FC
    • 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 a Core profile with GL version 3.1
    • 3.1FC - select a Core+Forward Compatible profile with GL version 3.1
  • 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 (if that variable is set), or else within .cache/mesa 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 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
  • 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
  • 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 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.
• See the driver code for other, lesser-used variables.

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.