[Mesa-dev] [PATCH 1/2] radeonsi: add support for an on-disk shader cache
Marek Olšák
maraeo at gmail.com
Sat Feb 25 19:43:06 UTC 2017
On Sat, Feb 25, 2017 at 5:06 PM, Dieter Nützel <Dieter at nuetzel-hh.de> wrote:
> Am 25.02.2017 05:56, schrieb Timothy Arceri:
>>
>> On 24/02/17 21:02, Marek Olšák wrote:
>>>
>>> On Fri, Feb 24, 2017 at 3:18 AM, Timothy Arceri <tarceri at itsqueeze.com>
>>> wrote:
>>>>
>>>>
>>>>
>>>> On 24/02/17 08:49, Timothy Arceri wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On 24/02/17 05:12, Marek Olšák wrote:
>>>>>>
>>>>>>
>>>>>> On Thu, Feb 23, 2017 at 3:09 AM, Timothy Arceri
>>>>>> <tarceri at itsqueeze.com> wrote:
>>>>>>>
>>>>>>>
>>>>>>> From: kdj0c <kdj0c at djinvi.net>
>>>>>>>
>>>>>>> V2 (Timothy Arceri):
>>>>>>> - when loading from disk cache also binary insert into memory cache.
>>>>>>> - check that the binary loaded from disk is the correct size. If not
>>>>>>> delete the cache item and skip loading from cache.
>>>>>>> ---
>>>>>>> src/gallium/drivers/radeonsi/si_state_shaders.c | 69
>>>>>>> ++++++++++++++++++++++---
>>>>>>> 1 file changed, 62 insertions(+), 7 deletions(-)
>>>>>>>
>>>>>>> diff --git a/src/gallium/drivers/radeonsi/si_state_shaders.c
>>>>>>> b/src/gallium/drivers/radeonsi/si_state_shaders.c
>>>>>>> index f615aa8..71556f9 100644
>>>>>>> --- a/src/gallium/drivers/radeonsi/si_state_shaders.c
>>>>>>> +++ b/src/gallium/drivers/radeonsi/si_state_shaders.c
>>>>>>> @@ -36,6 +36,9 @@
>>>>>>> #include "util/u_memory.h"
>>>>>>> #include "util/u_prim.h"
>>>>>>>
>>>>>>> +#include "util/disk_cache.h"
>>>>>>> +#include "util/mesa-sha1.h"
>>>>>>> +
>>>>>>> /* SHADER_CACHE */
>>>>>>>
>>>>>>> /**
>>>>>>> @@ -182,10 +185,12 @@ static bool si_load_shader_binary(struct
>>>>>>> si_shader *shader, void *binary)
>>>>>>> */
>>>>>>> static bool si_shader_cache_insert_shader(struct si_screen *sscreen,
>>>>>>> void *tgsi_binary,
>>>>>>> - struct si_shader *shader)
>>>>>>> + struct si_shader *shader,
>>>>>>> + bool
>>>>>>> insert_into_disk_cache)
>>>>>>> {
>>>>>>> void *hw_binary;
>>>>>>> struct hash_entry *entry;
>>>>>>> + uint8_t key[CACHE_KEY_SIZE];
>>>>>>>
>>>>>>> entry = _mesa_hash_table_search(sscreen->shader_cache,
>>>>>>> tgsi_binary);
>>>>>>> if (entry)
>>>>>>> @@ -201,6 +206,12 @@ static bool si_shader_cache_insert_shader(struct
>>>>>>> si_screen *sscreen,
>>>>>>> return false;
>>>>>>> }
>>>>>>>
>>>>>>> + if (sscreen->b.disk_shader_cache && insert_into_disk_cache) {
>>>>>>> + _mesa_sha1_compute(tgsi_binary, *((uint32_t
>>>>>>> *)tgsi_binary), key);
>>>>>>
>>>>>>
>>>>>>
>>>>>> What happens if we randomly get a sha1 collision?
>>>>>
>>>>>
>>>>>
>>>>> You should stop playing your game which will be rendering incorrectly
>>>>> and by a lotto ticket.
>>>>>
>>>>>> Shouldn't we store the whole key as well?
>>>>>
>>>>>
>>>>>
>>>>> Sure I can add that, its cheap to check here anyway. Although the other
>>>>> cache stages rely on a collision being improbable.
>>>>
>>>>
>>>>
>>>>
>>>> For some reason I thought the key was simpler than it is. It seems
>>>> excessive
>>>> to store and compare the tgsi again. I don't think git even worries
>>>> about
>>>> the possibility of a collision and we will be dealing with much smaller
>>>> amounts of cache items then commits in a git repository.
>>>>
>>>> Thoughts?
>>>
>>>
>>> I'll let others comment on this. If nobody comments, checking only the
>>> key can stay.
>>
>>
>> Seems SVN didn't used to worry about collisions either.
>>
>>
>> https://arstechnica.com/security/2017/02/watershed-sha1-collision-just-broke-the-webkit-repository-others-may-follow/
>
>
> Shouldn't sha1 _completely_ avoided, then?
We don't use SHA1 for security.
I guess there were problems with SVN before, they just weren't given
any publicity. It's an SVN bug, not a SHA1 issue.
Marek
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