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 verboseadditional 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
    glXSwapBufferscalls 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_ENUMerror, a corresponding error message indicating where the error occurred, and possibly why, will be printed to stderr. For release builds,MESA_DEBUGdefaults to off (no debug output).MESA_DEBUGaccepts the following comma-separated list of named flags, which adds extra behaviour to just setMESA_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 (orMESA_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_PROGvariable as well.
- MESA_EXTENSION_OVERRIDE
- can be used to enable/disable extensions. A value such as
    GL_EXT_foo -GL_EXT_barwill enable theGL_EXT_fooextension and disable theGL_EXT_barextension.
- MESA_EXTENSION_MAX_YEAR
- The GL_EXTENSIONSstring 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]
- FCis an optional suffix that indicates a forward compatible context. This is only valid for versions >= 3.0.
- COMPATis an optional suffix that indicates a compatibility context or- GL_ARB_compatibilitysupport. 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_compatibilityextension 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_compatibilityenabled per the driver default.
- 3.1FC
- select GL version 3.1 with forward compatibility and
        GL_ARB_compatibilitydisabled.
- 3.1COMPAT
- select GL version 3.1 with GL_ARB_compatibilityenabled.
- 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)
 
- The format should be 
- 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)
 
-  The format should be 
- MESA_GLSL_VERSION_OVERRIDE
- changes the value returned by
    glGetString(GL_SHADING_LANGUAGE_VERSION). Valid values are integers, such as130. 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, orGto 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_cachewithin 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_PATHand- 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)
 
- The format should be 
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
    pixmaporximage
- 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
- 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=helpand run e.g.glxgearsfor 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_VISIBLEtofalseandGALLIUM_HUD_TOGGLE_SIGNALto10(SIGUSR1). Usekill -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=truefor choosing one of the software rendererssoftpipe,llvmpipeorswr.
- 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. Seesrc/mesa/state_tracker/st_debug.cfor 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.logfile, such as the OpenGL program's name and command line arguments.
- SVGA_NO_LOGGING
- if set, disables logging to the vmware.logfile. 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 towglSwapIntervalEXT()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.