[Mesa-stable] [Mesa-dev] [PATCH 1/2] disk_cache: reduce default cache size to 5% of filesystem

[Michel Dänzer]

On 28/04/17 09:11 PM, Marek Olšák wrote:
> On Thu, Apr 27, 2017 at 8:47 AM, Michel Dänzer <michel at daenzer.net> wrote:
>> On 27/04/17 10:15 AM, Timothy Arceri wrote:
>>> Modern disks are extremely large and are only going to get bigger.
>>> Usage has shown frequent Mesa upgrades can result in the cache
>>> growing very fast i.e. wasting a lot of disk space unnecessarily.
>>>
>>> 5% seems like a more reasonable default.
>>>
>>> Cc: "17.1" <mesa-stable at lists.freedesktop.org>
>>> ---
>>>  src/util/disk_cache.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
>>> index d9de8ef..9fd7b96 100644
>>> --- a/src/util/disk_cache.c
>>> +++ b/src/util/disk_cache.c
>>> @@ -324,24 +324,24 @@ disk_cache_create(const char *gpu_name, const char *timestamp)
>>>           case '\0':
>>>           case 'G':
>>>           case 'g':
>>>           default:
>>>              max_size *= 1024*1024*1024;
>>>              break;
>>>           }
>>>        }
>>>     }
>>>
>>> -   /* Default to 1GB or 10% of filesystem for maximum cache size. */
>>> +   /* Default to 1GB or 5% of filesystem for maximum cache size. */
>>>     if (max_size == 0) {
>>>        statvfs(path, &vfs);
>>> -      max_size = MAX2(1024*1024*1024, vfs.f_blocks * vfs.f_bsize / 10);
>>> +      max_size = MAX2(1024*1024*1024, vfs.f_blocks * vfs.f_bsize / 20);
>>>     }
>>
>> 5% can still be quite a lot (what if every library on the system tried
>> using that much for itself?). How about 1%?
> 
> The argument is flawed. My ccache uses 12% (26.8 GB) of my disk, and
> I'm not saying "what if every small app used that much...". There is a
> very good reason for that size with my use case.

ccache defaults to a maximum cache size of 5G. You had to explicitly
allow it to use more; you can do the same with the Mesa shader cache.


> It certainly makes sense to use 5% of the filesystem for Mesa.

I don't agree for the default, especially as long as the Mesa shader
cache only actually makes use of about 10-20% of the disk space
allocated for it, due to having a huge number of tiny files. (ccache in
contrast actually makes good use of the disk space allocated for it,
because its cache entries are normally larger than a single disk block)


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer