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| author | John Firebaugh <john.firebaugh@gmail.com> | 2016-02-09 17:19:27 -0800 |
|---|---|---|
| committer | John Firebaugh <john.firebaugh@gmail.com> | 2016-02-10 15:40:20 -0800 |
| commit | db3620c58f0c3351e26b0e3bcfd23ff414f829a1 (patch) | |
| tree | e8def564e12307a997270b66a4ed46b68f5e13a4 /include/mbgl/util | |
| parent | 591012401072e63b89071787d90bf5ae4362dca1 (diff) | |
| download | qtlocation-mapboxgl-db3620c58f0c3351e26b0e3bcfd23ff414f829a1.tar.gz | |
[core] Implement an eviction policy for OfflineDatabase
When inserting an cached resource, or removing a region, remove least-recently used resources and tiles, not used by offline regions, until the used database size, as calculated by multiplying the number of in-use pages by the page size, is less than the maximum cache size minus 5 times the page size.
In addition, OfflineDatabase may be configured to ignore cache puts of individual resources larger than a certain size.
This policy is similar but not identical to the former SQLiteCache policy:
* It accounts for offline, by exempting resources required by offline regions from eviction.
* It must delete from two tables (resources and tiles), rather than one. Currently the strategy is naive: evict 50 rows at a time from each table.
* It makes maximumCacheSize and maximumCacheEntrySize completely independent. The SQLiteCache implementation evicted when `usedSize > maximumCacheSize - 2 * maximumCacheEntrySize`. This evicts when `usedSize > maximumCacheSize - 5 * pageSize`.
* It uses a non-unlimited default value for maximumCacheSize: 50 MB. We should have always had a limit in place; "a cache without an eviction policy is a resource leak".
Diffstat (limited to 'include/mbgl/util')
| -rw-r--r-- | include/mbgl/util/constants.hpp | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/mbgl/util/constants.hpp b/include/mbgl/util/constants.hpp index 24f4b5ee72..667e2f8497 100644 --- a/include/mbgl/util/constants.hpp +++ b/include/mbgl/util/constants.hpp @@ -21,6 +21,9 @@ extern const double PITCH_MAX; extern const double MIN_ZOOM; extern const double MAX_ZOOM; +extern const uint64_t DEFAULT_MAX_CACHE_SIZE; +extern const uint64_t DEFAULT_MAX_CACHE_ENTRY_SIZE; + } // namespace util namespace debug { |