docs/envvars.html

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  11   The Mesa 3D Graphics Library
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  16
  17 <h1>Environment Variables</h1>
  18
  19 <p>
  20 Normally, no environment variables need to be set.  Most of the environment
  21 variables used by Mesa/Gallium are for debugging purposes, but they can
  22 sometimes be useful for debugging end-user issues.
  23 </p>
  24
  25
  26 <h2>LibGL environment variables</h2>
  27
  28 <dl>
  29 <dt>LIBGL_DEBUG</dt>
  30 <dd>If defined debug information will be printed to stderr.
  31     If set to 'verbose' additional information will be printed.</dd>
  32 <dt>LIBGL_DRIVERS_PATH</dt>
  33 <dd>colon-separated list of paths to search for DRI drivers</dd>
  34 <dt>LIBGL_ALWAYS_INDIRECT</dt>
  35 <dd>if set to `true`, forces an indirect rendering context/connection.</dd>
  36 <dt>LIBGL_ALWAYS_SOFTWARE</dt>
  37 <dd>if set to `true`, always use software rendering</dd>
  38 <dt>LIBGL_NO_DRAWARRAYS</dt>
  39 <dd>if set to `true`, do not use DrawArrays GLX protocol (for debugging)</dd>
  40 <dt>LIBGL_SHOW_FPS</dt>
  41 <dd>print framerate to stdout based on the number of glXSwapBuffers
  42     calls per second.</dd>
  43 <dt>LIBGL_DRI3_DISABLE</dt>
  44 <dd>disable DRI3 if set to `true`.</dd>
  45 </dl>
  46
  47 <h2>Core Mesa environment variables</h2>
  48
  49 <dl>
  50 <dt>MESA_NO_ASM</dt>
  51 <dd>if set, disables all assembly language optimizations</dd>
  52 <dt>MESA_NO_MMX</dt>
  53 <dd>if set, disables Intel MMX optimizations</dd>
  54 <dt>MESA_NO_3DNOW</dt>
  55 <dd>if set, disables AMD 3DNow! optimizations</dd>
  56 <dt>MESA_NO_SSE</dt>
  57 <dd>if set, disables Intel SSE optimizations</dd>
  58 <dt>MESA_NO_ERROR</dt>
  59 <dd>if set to 1, error checking is disabled as per KHR_no_error.
  60     This will result in undefined behaviour for invalid use of the api, but
  61     can reduce CPU use for apps that are known to be error free.</dd>
  62 <dt>MESA_DEBUG</dt>
  63 <dd>if set, error messages are printed to stderr.  For example,
  64     if the application generates a GL_INVALID_ENUM error, a corresponding error
  65     message indicating where the error occurred, and possibly why, will be
  66     printed to stderr. For release builds, MESA_DEBUG defaults to off (no debug
  67     output). MESA_DEBUG accepts the following comma-separated list of named
  68     flags, which adds extra behaviour to just set MESA_DEBUG=1:
  69     <dl>
  70       <dt>silent</dt>
  71       <dd>turn off debug messages. Only useful for debug builds.</dd>
  72       <dt>flush</dt>
  73       <dd>flush after each drawing command</dd>
  74       <dt>incomplete_tex</dt>
  75       <dd>extra debug messages when a texture is incomplete</dd>
  76       <dt>incomplete_fbo</dt>
  77       <dd>extra debug messages when a fbo is incomplete</dd>
  78       <dt>context</dt>
  79       <dd>create a debug context (see GLX_CONTEXT_DEBUG_BIT_ARB) and print
  80           error and performance messages to stderr (or MESA_LOG_FILE).</dd>
  81     </dl>
  82 </dd>
  83 <dt>MESA_LOG_FILE</dt>
  84 <dd>specifies a file name for logging all errors, warnings,
  85     etc., rather than stderr</dd>
  86 <dt>MESA_TEX_PROG</dt>
  87 <dd>if set, implement conventional texture env modes with
  88     fragment programs (intended for developers only)</dd>
  89 <dt>MESA_TNL_PROG</dt>
  90 <dd>if set, implement conventional vertex transformation operations with
  91     vertex programs (intended for developers only). Setting this variable
  92     automatically sets the MESA_TEX_PROG variable as well.</dd>
  93 <dt>MESA_EXTENSION_OVERRIDE</dt>
  94 <dd>can be used to enable/disable extensions. A value such as
  95     "GL_EXT_foo -GL_EXT_bar" will enable the GL_EXT_foo extension and disable
  96     the GL_EXT_bar extension.</dd>
  97 <dt>MESA_EXTENSION_MAX_YEAR</dt>
  98 <dd>The GL_EXTENSIONS string returned by Mesa is sorted by extension year.
  99     If this variable is set to year X, only extensions defined on or before
 100     year X will be reported. This is to work-around a bug in some games where
 101     the extension string is copied into a fixed-size buffer without
 102     truncating. If the extension string is too long, the buffer overrun can
 103     cause the game to crash. This is a work-around for that.
 104 </dd>
 105 <dt>MESA_GL_VERSION_OVERRIDE</dt>
 106 <dd>changes the value returned by
 107 glGetString(GL_VERSION) and possibly the GL API type.
 108 <ul>
 109   <li>The format should be MAJOR.MINOR[FC|COMPAT]
 110   <li>FC is an optional suffix that indicates a forward compatible
 111       context. This is only valid for versions &gt;= 3.0.
 112   <li>COMPAT is an optional suffix that indicates a compatibility
 113       context or GL_ARB_compatibility support. This is only valid for
 114       versions &gt;= 3.1.
 115   <li>GL versions &lt;= 3.0 are set to a compatibility (non-Core)
 116       profile
 117   <li>GL versions = 3.1, depending on the driver, it may or may not
 118       have the ARB_compatibility extension enabled.
 119   <li>GL versions &gt;= 3.2 are set to a Core profile
 120   <li>Examples:
 121   <dl>
 122     <dt>2.1</dt>
 123     <dd>select a compatibility (non-Core) profile with GL version 2.1.</dd>
 124     <dt>3.0</dt>
 125     <dd>select a compatibility (non-Core) profile with GL version 3.0.</dd>
 126     <dt>3.0FC</dt>
 127     <dd>select a Core+Forward Compatible profile with GL version 3.0.</dd>
 128     <dt>3.1</dt>
 129     <dd>select GL version 3.1 with GL_ARB_compatibility enabled per the
 130         driver default.</dd>
 131     <dt>3.1FC</dt>
 132     <dd>select GL version 3.1 with forward compatibility and
 133         GL_ARB_compatibility disabled.</dd>
 134     <dt>3.1COMPAT</dt>
 135     <dd>select GL version 3.1 with GL_ARB_compatibility enabled.</dd>
 136     <dt>X.Y</dt>
 137     <dd>override GL version to X.Y without changing the profile.</dd>
 138     <dt>X.YFC</dt>
 139     <dd>select a Core+Forward Compatible profile with GL version X.Y.</dd>
 140     <dt>X.YCOMPAT</dt>
 141     <dd>select a Compatibility profile with GL version X.Y.</dd>
 142   </dl>
 143   <li>Mesa may not really implement all the features of the given
 144       version. (for developers only)
 145 </ul>
 146 </dd>
 147 <dt>MESA_GLES_VERSION_OVERRIDE</dt>
 148 <dd>changes the value returned by glGetString(GL_VERSION) for OpenGL ES.
 149 <ul>
 150 <li> The format should be MAJOR.MINOR
 151 <li> Examples: 2.0, 3.0, 3.1
 152 <li> Mesa may not really implement all the features of the given version.
 153 (for developers only)
 154 </ul>
 155 </dd>
 156 <dt>MESA_GLSL_VERSION_OVERRIDE</dt>
 157 <dd>changes the value returned by glGetString(GL_SHADING_LANGUAGE_VERSION).
 158     Valid values are integers, such as "130".  Mesa will not really implement
 159     all the features of the given language version if it's higher than what's
 160     normally reported. (for developers only)
 161 </dd>
 162 <dt>MESA_GLSL_CACHE_DISABLE</dt>
 163 <dd>if set to `true`, disables the GLSL shader cache</dd>
 164 <dt>MESA_GLSL_CACHE_MAX_SIZE</dt>
 165 <dd>if set, determines the maximum size of the on-disk cache of compiled GLSL
 166     programs. Should be set to a number optionally followed by 'K', 'M', or
 167     'G' to specify a size in kilobytes, megabytes, or gigabytes. By default,
 168     gigabytes will be assumed. And if unset, a maximum size of 1GB will be
 169     used. Note: A separate cache might be created for each architecture that
 170     Mesa is installed for on your system. For example under the default
 171     settings you may end up with a 1GB cache for x86_64 and another 1GB cache
 172     for i386.</dd>
 173 <dt>MESA_GLSL_CACHE_DIR</dt>
 174 <dd>if set, determines the directory to be used for the on-disk cache of
 175     compiled GLSL programs. If this variable is not set, then the cache will
 176     be stored in $XDG_CACHE_HOME/mesa_shader_cache (if that variable is set),
 177     or else within .cache/mesa_shader_cache within the user's home directory.
 178 </dd>
 179 <dt>MESA_GLSL</dt>
 180 <dd><a href="shading.html#envvars">shading language compiler options</a></dd>
 181 <dt>MESA_NO_MINMAX_CACHE</dt>
 182 <dd>when set, the minmax index cache is globally disabled.</dd>
 183 <dt>MESA_SHADER_CAPTURE_PATH</dt>
 184 <dd>see <a href="shading.html#capture">Capturing Shaders</a></dd>
 185 <dt>MESA_SHADER_DUMP_PATH and MESA_SHADER_READ_PATH</dt>
 186 <dd>see <a href="shading.html#replacement">Experimenting with Shader Replacements</a></dd>
 187 <dt>MESA_VK_VERSION_OVERRIDE</dt>
 188 <dd>changes the Vulkan physical device version
 189     as returned in VkPhysicalDeviceProperties::apiVersion.
 190   <ul>
 191     <li>The format should be MAJOR.MINOR[.PATCH]</li>
 192     <li>This will not let you force a version higher than the driver's
 193         instance versionas advertised by vkEnumerateInstanceVersion</li>
 194     <li>This can be very useful for debugging but some features may not be
 195         implemented correctly. (For developers only)</li>
 196   </ul>
 197 </dd>
 198 </dl>
 199
 200
 201 <h2>Mesa Xlib driver environment variables</h2>
 202
 203 <p>
 204 The following are only applicable to the Mesa Xlib software driver.
 205 See the <a href="xlibdriver.html">Xlib software driver page</a> for details.
 206 </p>
 207 <dl>
 208 <dt>MESA_RGB_VISUAL</dt>
 209 <dd>specifies the X visual and depth for RGB mode</dd>
 210 <dt>MESA_CI_VISUAL</dt>
 211 <dd>specifies the X visual and depth for CI mode</dd>
 212 <dt>MESA_BACK_BUFFER</dt>
 213 <dd>specifies how to implement the back color buffer, either "pixmap" or
 214     "ximage"</dd>
 215 <dt>MESA_GAMMA</dt>
 216 <dd>gamma correction coefficients for red, green, blue channels</dd>
 217 <dt>MESA_XSYNC</dt>
 218 <dd>enable synchronous X behavior (for debugging only)</dd>
 219 <dt>MESA_GLX_FORCE_CI</dt>
 220 <dd>if set, force GLX to treat 8bpp visuals as CI visuals</dd>
 221 <dt>MESA_GLX_FORCE_ALPHA</dt>
 222 <dd>if set, forces RGB windows to have an alpha channel.</dd>
 223 <dt>MESA_GLX_DEPTH_BITS</dt>
 224 <dd>specifies default number of bits for depth buffer.</dd>
 225 <dt>MESA_GLX_ALPHA_BITS</dt>
 226 <dd>specifies default number of bits for alpha channel.</dd>
 227 </dl>
 228
 229
 230 <h2>i945/i965 driver environment variables (non-Gallium)</h2>
 231
 232 <dl>
 233 <dt>INTEL_NO_HW</dt>
 234 <dd>if set to 1, prevents batches from being submitted to the hardware.
 235     This is useful for debugging hangs, etc.</dd>
 236 <dt>INTEL_DEBUG</dt>
 237 <dd>a comma-separated list of named flags, which do various things:
 238 <dl>
 239    <dt>ann</dt>
 240    <dd>annotate IR in assembly dumps</dd>
 241    <dt>aub</dt>
 242    <dd>dump batches into an AUB trace for use with simulation tools</dd>
 243    <dt>bat</dt>
 244    <dd>emit batch information</dd>
 245    <dt>blit</dt>
 246    <dd>emit messages about blit operations</dd>
 247    <dt>blorp</dt>
 248    <dd>emit messages about the blorp operations (blits &amp; clears)</dd>
 249    <dt>buf</dt>
 250    <dd>emit messages about buffer objects</dd>
 251    <dt>clip</dt>
 252    <dd>emit messages about the clip unit (for old gens, includes the CLIP program)</dd>
 253    <dt>color</dt>
 254    <dd>use color in output</dd>
 255    <dt>cs</dt>
 256    <dd>dump shader assembly for compute shaders</dd>
 257    <dt>do32</dt>
 258    <dd>generate compute shader SIMD32 programs even if workgroup size doesn't exceed the SIMD16 limit</dd>
 259    <dt>dri</dt>
 260    <dd>emit messages about the DRI interface</dd>
 261    <dt>fbo</dt>
 262    <dd>emit messages about framebuffers</dd>
 263    <dt>fs</dt>
 264    <dd>dump shader assembly for fragment shaders</dd>
 265    <dt>gs</dt>
 266    <dd>dump shader assembly for geometry shaders</dd>
 267    <dt>hex</dt>
 268    <dd>print instruction hex dump with the disassembly</dd>
 269    <dt>l3</dt>
 270    <dd>emit messages about the new L3 state during transitions</dd>
 271    <dt>miptree</dt>
 272    <dd>emit messages about miptrees</dd>
 273    <dt>no8</dt>
 274    <dd>don't generate SIMD8 fragment shader</dd>
 275    <dt>no16</dt>
 276    <dd>suppress generation of 16-wide fragment shaders. useful for debugging broken shaders</dd>
 277    <dt>nocompact</dt>
 278    <dd>disable instruction compaction</dd>
 279    <dt>nodualobj</dt>
 280    <dd>suppress generation of dual-object geometry shader code</dd>
 281    <dt>norbc</dt>
 282    <dd>disable single sampled render buffer compression</dd>
 283    <dt>optimizer</dt>
 284    <dd>dump shader assembly to files at each optimization pass and iteration that make progress</dd>
 285    <dt>perf</dt>
 286    <dd>emit messages about performance issues</dd>
 287    <dt>perfmon</dt>
 288    <dd>emit messages about AMD_performance_monitor</dd>
 289    <dt>pix</dt>
 290    <dd>emit messages about pixel operations</dd>
 291    <dt>prim</dt>
 292    <dd>emit messages about drawing primitives</dd>
 293    <dt>reemit</dt>
 294    <dd>mark all state dirty on each draw call</dd>
 295    <dt>sf</dt>
 296    <dd>emit messages about the strips &amp; fans unit (for old gens, includes the SF program)</dd>
 297    <dt>shader_time</dt>
 298    <dd>record how much GPU time is spent in each shader</dd>
 299    <dt>spill_fs</dt>
 300    <dd>force spilling of all registers in the scalar backend (useful to debug spilling code)</dd>
 301    <dt>spill_vec4</dt>
 302    <dd>force spilling of all registers in the vec4 backend (useful to debug spilling code)</dd>
 303    <dt>state</dt>
 304    <dd>emit messages about state flag tracking</dd>
 305    <dt>submit</dt>
 306    <dd>emit batchbuffer usage statistics</dd>
 307    <dt>sync</dt>
 308    <dd>after sending each batch, emit a message and wait for that batch to finish rendering</dd>
 309    <dt>tcs</dt>
 310    <dd>dump shader assembly for tessellation control shaders</dd>
 311    <dt>tes</dt>
 312    <dd>dump shader assembly for tessellation evaluation shaders</dd>
 313    <dt>tex</dt>
 314    <dd>emit messages about textures.</dd>
 315    <dt>urb</dt>
 316    <dd>emit messages about URB setup</dd>
 317    <dt>vert</dt>
 318    <dd>emit messages about vertex assembly</dd>
 319    <dt>vs</dt>
 320    <dd>dump shader assembly for vertex shaders</dd>
 321 </dl>
 322 </dd>
 323 <dt>INTEL_SCALAR_VS (or TCS, TES, GS)</dt>
 324 <dd>force scalar/vec4 mode for a shader stage (Gen8-9 only)</dd>
 325 <dt>INTEL_PRECISE_TRIG</dt>
 326 <dd>if set to 1, true or yes, then the driver prefers accuracy over
 327     performance in trig functions.</dd>
 328 </dl>
 329
 330
 331 <h2>Radeon driver environment variables (radeon, r200, and r300g)</h2>
 332
 333 <dl>
 334 <dt>RADEON_NO_TCL</dt>
 335 <dd>if set, disable hardware-accelerated Transform/Clip/Lighting.</dd>
 336 </dl>
 337
 338
 339 <h2>EGL environment variables</h2>
 340
 341 <p>
 342 Mesa EGL supports different sets of environment variables.  See the
 343 <a href="egl.html">Mesa EGL</a> page for the details.
 344 </p>
 345
 346
 347 <h2>Gallium environment variables</h2>
 348
 349 <dl>
 350 <dt>GALLIUM_HUD</dt>
 351 <dd>draws various information on the screen, like framerate,
 352     cpu load, driver statistics, performance counters, etc.
 353     Set GALLIUM_HUD=help and run e.g. glxgears for more info.</dd>
 354 <dt>GALLIUM_HUD_PERIOD</dt>
 355 <dd>sets the hud update rate in seconds (float). Use zero
 356     to update every frame. The default period is 1/2 second.</dd>
 357 <dt>GALLIUM_HUD_VISIBLE</dt>
 358 <dd>control default visibility, defaults to true.</dd>
 359 <dt>GALLIUM_HUD_TOGGLE_SIGNAL</dt>
 360 <dd>toggle visibility via user specified signal.
 361     Especially useful to toggle hud at specific points of application and
 362     disable for unencumbered viewing the rest of the time. For example, set
 363     GALLIUM_HUD_VISIBLE to false and GALLIUM_HUD_TOGGLE_SIGNAL to 10 (SIGUSR1).
 364     Use kill -10 &lt;pid&gt; to toggle the hud as desired.</dd>
 365 <dt>GALLIUM_HUD_DUMP_DIR</dt>
 366 <dd>specifies a directory for writing the displayed hud values into files.</dd>
 367 <dt>GALLIUM_DRIVER</dt>
 368 <dd>useful in combination with LIBGL_ALWAYS_SOFTWARE=true for choosing one
 369     of the software renderers "softpipe", "llvmpipe" or "swr".</dd>
 370 <dt>GALLIUM_LOG_FILE</dt>
 371 <dd>specifies a file for logging all errors, warnings, etc.
 372     rather than stderr.</dd>
 373 <dt>GALLIUM_PRINT_OPTIONS</dt>
 374 <dd>if non-zero, print all the Gallium environment variables which are
 375     used, and their current values.</dd>
 376 <dt>GALLIUM_DUMP_CPU</dt>
 377 <dd>if non-zero, print information about the CPU on start-up</dd>
 378 <dt>TGSI_PRINT_SANITY</dt>
 379 <dd>if set, do extra sanity checking on TGSI shaders and
 380     print any errors to stderr.</dd>
 381 <dt>DRAW_FSE</dt>
 382 <dd>???</dd>
 383 <dt>DRAW_NO_FSE</dt>
 384 <dd>???</dd>
 385 <dt>DRAW_USE_LLVM</dt>
 386 <dd>if set to zero, the draw module will not use LLVM to execute
 387     shaders, vertex fetch, etc.</dd>
 388 <dt>ST_DEBUG</dt>
 389 <dd>controls debug output from the Mesa/Gallium state tracker.
 390     Setting to "tgsi", for example, will print all the TGSI shaders.
 391     See src/mesa/state_tracker/st_debug.c for other options.</dd>
 392 </dl>
 393
 394 <h3>Clover state tracker environment variables</h3>
 395
 396 <dl>
 397 <dt>CLOVER_EXTRA_BUILD_OPTIONS</dt>
 398 <dd>allows specifying additional compiler and linker
 399     options. Specified options are appended after the options set by the OpenCL
 400     program in clBuildProgram.</dd>
 401 <dt>CLOVER_EXTRA_COMPILE_OPTIONS</dt>
 402 <dd>allows specifying additional compiler
 403     options. Specified options are appended after the options set by the OpenCL
 404     program in clCompileProgram.</dd>
 405 <dt>CLOVER_EXTRA_LINK_OPTIONS</dt>
 406 <dd>allows specifying additional linker
 407     options. Specified options are appended after the options set by the OpenCL
 408     program in clLinkProgram.</dd>
 409 </dl>
 410
 411
 412 <h3>Softpipe driver environment variables</h3>
 413 <dl>
 414 <dt>SOFTPIPE_DUMP_FS</dt>
 415 <dd>if set, the softpipe driver will print fragment shaders to stderr</dd>
 416 <dt>SOFTPIPE_DUMP_GS</dt>
 417 <dd>if set, the softpipe driver will print geometry shaders to stderr</dd>
 418 <dt>SOFTPIPE_NO_RAST</dt>
 419 <dd>if set, rasterization is no-op'd.  For profiling purposes.</dd>
 420 <dt>SOFTPIPE_USE_LLVM</dt>
 421 <dd>if set, the softpipe driver will try to use LLVM JIT for
 422     vertex shading processing.</dd>
 423 </dl>
 424
 425
 426 <h3>LLVMpipe driver environment variables</h3>
 427 <dl>
 428 <dt>LP_NO_RAST</dt>
 429 <dd>if set LLVMpipe will no-op rasterization</dd>
 430 <dt>LP_DEBUG</dt>
 431 <dd>a comma-separated list of debug options is accepted.  See the
 432     source code for details.</dd>
 433 <dt>LP_PERF</dt>
 434 <dd>a comma-separated list of options to selectively no-op various
 435     parts of the driver.  See the source code for details.</dd>
 436 <dt>LP_NUM_THREADS</dt>
 437 <dd>an integer indicating how many threads to use for rendering.
 438     Zero turns off threading completely.  The default value is the number of CPU
 439     cores present.</dd>
 440 </dl>
 441
 442 <h3>VMware SVGA driver environment variables</h3>
 443 <dl>
 444 <dt>SVGA_FORCE_SWTNL</dt>
 445 <dd>force use of software vertex transformation</dd>
 446 <dt>SVGA_NO_SWTNL</dt>
 447 <dd>don't allow software vertex transformation fallbacks (will often result
 448     in incorrect rendering).</dd>
 449 <dt>SVGA_DEBUG</dt>
 450 <dd>for dumping shaders, constant buffers, etc.  See the code for
 451     details.</dd>
 452 <dt>SVGA_EXTRA_LOGGING</dt>
 453 <dd>if set, enables extra logging to the vmware.log file, such as the
 454     OpenGL program's name and command line arguments.</dd>
 455 <dt>SVGA_NO_LOGGING</dt>
 456 <dd>if set, disables logging to the vmware.log file. This is useful when
 457     using Valgrind because it otherwise crashes when initializing the host
 458     log feature.</dd>
 459 </dl>
 460 <p>See the driver code for other, lesser-used variables.</p>
 461
 462 <h3>WGL environment variables</h3>
 463 <dl>
 464 <dt>WGL_SWAP_INTERVAL</dt>
 465 <dd>to set a swap interval, equivalent to calling wglSwapIntervalEXT()
 466     in an application.  If this environment variable is set, application
 467     calls to wglSwapIntervalEXT() will have no effect.</dd>
 468 </dl>
 469
 470 <h3>VA-API state tracker environment variables</h3>
 471 <dl>
 472 <dt>VAAPI_MPEG4_ENABLED</dt>
 473 <dd>enable MPEG4 for VA-API, disabled by default.</dd>
 474 </dl>
 475
 476
 477 <h3>VC4 driver environment variables</h3>
 478 <dl>
 479 <dt>VC4_DEBUG</dt>
 480 <dd>a comma-separated list of named flags, which do various things:
 481 <dl>
 482    <dt>cl</dt>
 483    <dd>dump command list during creation</dd>
 484    <dt>qpu</dt>
 485    <dd>dump generated QPU instructions</dd>
 486    <dt>qir</dt>
 487    <dd>dump QPU IR during program compile</dd>
 488    <dt>nir</dt>
 489    <dd>dump NIR during program compile</dd>
 490    <dt>tgsi</dt>
 491    <dd>dump TGSI during program compile</dd>
 492    <dt>shaderdb</dt>
 493    <dd>dump program compile information for shader-db analysis</dd>
 494    <dt>perf</dt>
 495    <dd>print during performance-related events</dd>
 496    <dt>norast</dt>
 497    <dd>skip actual hardware execution of commands</dd>
 498    <dt>always_flush</dt>
 499    <dd>flush after each draw call</dd>
 500    <dt>always_sync</dt>
 501    <dd>wait for finish after each flush</dd>
 502    <dt>dump</dt>
 503    <dd>write a GPU command stream trace file (VC4 simulator only)</dd>
 504 </dl>
 505 </dd>
 506 </dl>
 507
 508
 509 <p>
 510 Other Gallium drivers have their own environment variables.  These may change
 511 frequently so the source code should be consulted for details.
 512 </p>
 513
 514 </div>
 515 </body>
 516 </html>