Whenever a single file mesa-db cache hits max size limit, a half of cache
is evicted and the cache file is defragmented. The downside of this eviction
strategy is that it causes high disk IO usage during eviction if mesa-db
cache file size is large.
In order to mitigate this downside, we will split mesa-db into multiple
part such that only one part will be evicted at a time. Each part will be
an individual single file mesa-db cache, like a DB shard. The new multipart
mesa-db cache will merge the parts into a single virtual cache.
This patch introduces two new environment variables:
1. MESA_DISK_CACHE_DATABASE_NUM_PARTS:
Controls number of mesa-db cache file parts. By default 50 parts will be
created. The old pre-multipart mesa-db cache files will be auto-removed
if they exist, i.e. Mesa will switch to the new DB version automatically.
2. MESA_DISK_CACHE_DATABASE_EVICTION_SCORE_2X_PERIOD:
Controls the eviction score doubling time period. The evicted DB part
selection is based on cache entries size weighted by 'last_access_time' of
the entries. By default the cache eviction score is doubled for each month
of cache entry age, i.e. for two equally sized entries where one entry is
older by one month than the other, the older entry will have x2 eviction
score than the other entry. Database part with a highest total eviction
score is selected for eviction.
This patch brings x40 performance improvement of cache eviction time using
multipart cache vs a single file cache due to a smaller eviction portions
and more optimized eviction algorithm.
Acked-by: Timothy Arceri <tarceri@itsqueeze.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20256>
Add support for removal of cache entries to mesa-db cache. This allows
to have a more predictable unit tests by removing dummy entries that
are added to cache when test-cache is created by unit-testing framework.
Acked-by: Timothy Arceri <tarceri@itsqueeze.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20256>
In order to ease writing mesa-db eviction unit tests, stop accounting
mesa-db cache file header size during checking whether cache file reached
the size limit. This change ensures that older unit tests will keep working
whenever cache header version/size will change.
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20256>
Introduce new cache type, the Mesa-DB. This is a single-file read/write
cache that is based on the read-only Fossilize DB cache. Mesa-DB supports
cache size capping. It's a much more efficient cache than the multi-file
cache because Mesa-DB doesn't have the inode overhead. The plan is to make
Mesa-DB the default cache implementation once it will be deemed as stable
and well tested. For now users have to set the new MESA_DISK_CACHE_DATABASE
environment variable in order to active the Mesa-DB cache.
Mesa-DB cache is resilient to corrupted cache files and doesn't require
maintenance from users and developers. The size capping is implemented
by evicting least recently used cache items and compacting the cache
database files with the evicted entries. In order to prevent frequent
compaction of the cache, at minimum a half of cache is evicted when cache
is full.
Acked-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16888>
