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.