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 - forces an indirect rendering context/connection.
• LIBGL_ALWAYS_SOFTWARE - if set, always use software rendering
• LIBGL_NO_DRAWARRAYS - if set 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 (the value does not matter)

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_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.
  If the value of MESA_DEBUG is 'FP' floating point arithmetic errors will generate exceptions.
• 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 - shading language compiler options
• MESA_NO_MINMAX_CACHE - when set, the minmax index cache is globally disabled.

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:
  • tex - emit messages about textures.
  • state - emit messages about state flag tracking
  • blit - emit messages about blit operations
  • miptree - emit messages about miptrees
  • perf - emit messages about performance issues
  • perfmon - emit messages about AMD_performance_monitor
  • bat - emit batch information
  • pix - emit messages about pixel operations
  • buf - emit messages about buffer objects
  • reg - emit messages about regions
  • fbo - emit messages about framebuffers
  • fs - dump shader assembly for fragment shaders
  • gs - dump shader assembly for geometry shaders
  • sync - emit messages about synchronization
  • prim - emit messages about drawing primitives
  • vert - emit messages about vertex assembly
  • dri - emit messages about the DRI interface
  • sf - emit messages about the strips & fans unit (for old gens, includes the SF program)
  • stats - enable statistics counters. you probably actually want perfmon or intel_gpu_top instead.
  • urb - emit messages about URB setup
  • vs - dump shader assembly for vertex shaders
  • clip - emit messages about the clip unit (for old gens, includes the CLIP program)
  • aub - dump batches into an AUB trace for use with simulation tools
  • shader_time - record how much GPU time is spent in each shader
  • no16 - suppress generation of 16-wide fragment shaders. useful for debugging broken shaders
  • blorp - emit messages about the blorp operations (blits & clears)
  • nodualobj - suppress generation of dual-object geometry shader code
  • optimizer - dump shader assembly to files at each optimization pass and iteration that make progress
  • vec4 - force vec4 mode in vertex 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)

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_SIGNAL_TOGGLE to 10 (SIGUSR1). Use kill -10 to toggle the hud as desired.
• 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.

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.
• 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.