[Mesa-dev] [PATCH v2 32/32] disk_cache: Add support for MESA_GLSL_CACHE_TIMESTAMP in debug builds

[Timothy Arceri]

Maybe add to docs?

On 19/10/17 16:32, Jordan Justen wrote:
> The MESA_GLSL_CACHE_TIMESTAMP environment variable can be set to
> override the driver timestamp. Usually the driver will specify a hash
> of their driver build so the cache items become invalid with each
> driver build.
> 
> We don't guarantee a stable serialized shader cache format, so
> changing the timestamp for each build is required for safety.
> 
> Nevertheless, during debug, making small changes to the driver may be
> known to be safe. The driver developer can use this variable to keep
> the timestamp consistent. When debugging issues on an application for
> which the shader cache greatly lowers the startup time, this can save
> the developer significant time.
> 
> Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
> ---
>   src/util/disk_cache.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
> index fde6e2e097..54f48a8ba5 100644
> --- a/src/util/disk_cache.c
> +++ b/src/util/disk_cache.c
> @@ -208,6 +208,18 @@ disk_cache_create(const char *gpu_name, const char *timestamp,
>      if (env_var_as_boolean("MESA_GLSL_CACHE_DISABLE", false))
>         goto fail;
>   
> +#ifdef DEBUG
> +   /* For debug builds, MESA_GLSL_CACHE_TIMESTAMP can be set to override the
> +    * driver specified timestamp. This will allow small changes to be made to
> +    * the driver without invalidating the cache. Given that this is normally
> +    * unsafe, it is only allowed for debug builds.
> +    */
> +   const char *timestamp_override = getenv("MESA_GLSL_CACHE_TIMESTAMP");
> +   if (timestamp_override) {
> +      timestamp = timestamp_override;
> +   }
> +#endif
> +
>      /* Determine path for cache based on the first defined name as follows:
>       *
>       *   $MESA_GLSL_CACHE_DIR
>