[Mesa-dev] [PATCH 2/4] util/disk_cache: add struct cache_item_metadata

[Timothy Arceri]

On 22/08/17 18:02, Michel Dänzer wrote:
> On 22/08/17 10:02 AM, Pierre-Loup A. Griffais wrote:
>> On 08/18/2017 04:02 AM, Nicolai Hähnle wrote:
>>> On 15.08.2017 01:26, Timothy Arceri wrote:
>>>> This will be used to store more information about the cache item
>>>> in it's header. This information is intended for 3rd party and
>>>> cache analysis use but can also be used for detecting the unlikely
>>>> scenario of cache collisions.
>>>> ---
>>>>    src/util/disk_cache.h | 22 ++++++++++++++++++++++
>>>>    1 file changed, 22 insertions(+)
>>>>
>>>> diff --git a/src/util/disk_cache.h b/src/util/disk_cache.h
>>>> index 9aade16a9e..d6d7609ffb 100644
>>>> --- a/src/util/disk_cache.h
>>>> +++ b/src/util/disk_cache.h
>>>> @@ -34,20 +34,42 @@
>>>>    #ifdef __cplusplus
>>>>    extern "C" {
>>>>    #endif
>>>>    /* Size of cache keys in bytes. */
>>>>    #define CACHE_KEY_SIZE 20
>>>>    typedef uint8_t cache_key[CACHE_KEY_SIZE];
>>>> +/* WARNING: 3rd party applications might be reading the cache item
>>>> metadata.
>>>> + * Do not change these values without making the change widely known.
>>>> + * Please contact Valve developers and make them aware of this change.
>>>> + */
>>>> +#define CACHE_ITEM_TYPE_UNKNOWN  0x0
>>>> +#define CACHE_ITEM_TYPE_GLSL     0x1
>>>> +
>>>> +typedef uint32_t cache_item_metadata_type;
>>>
>>> Please don't do typedefs like that, they just obfuscate. If you don't
>>> want to just use uint32_t, I'd suggest to use an enum.
>>>
>>> At a higher level, what is this actually good for? So I get Valve
>>> wants to parse something in the shader cache, but why / what for?
>>
>> Steam looks at local entries and delete leftover ones should you upgrade
>> Mesa or your GPU.
> 
> That's rather questionable. Steam should leave purging old cache entries
> to Mesa.

My understanding is steam overrides the environment var so that each 
game with have its own local cache. If they don't get cleaned up it 
could potentially waste a significant amount of space.