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Necko/MobileCache: Difference between revisions
→Collecting data to figure out why HTTP disk cache is slow on fennec
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So far we only have aggregate data (tp4 runs) that shows the cache is often a perf loss on mobile - see [[Necko/MobileCache#Effect_of_Cache_Size]]. | So far we only have aggregate data (tp4 runs) that shows the cache is often a perf loss on mobile - see [[Necko/MobileCache#Effect_of_Cache_Size]]. | ||
* bjarne: note that this test is limited in that it cyclically loads a limited pageset, and it keeps the memory-cache at 1Mb. Effectively it says "When loading a relatively small pageset over-and-over again on mobile, a 1Mb memory-cache is often more efficient than a disk-cache." Given that the cache-service prefers using a disk-cache over a memory-cache, and the memory-cache uses a more sophisticated replacement-algorithm than the disk-cache (see {{bug|648605}} and {{bug|693255}}) this is not surprising. To be more conclusive we need results from running this test with the memory-cache turned off. | * bjarne: note that this test is limited in that it cyclically loads a limited pageset, and it keeps the memory-cache at 1Mb. Effectively it says "When loading a relatively small pageset over-and-over again on mobile, a 1Mb memory-cache is often more efficient than a disk-cache." Given that the cache-service prefers using a disk-cache over a memory-cache, and the memory-cache uses a more sophisticated replacement-algorithm than the disk-cache (see {{bug|648605}} and {{bug|693255}}) this is not surprising. To be more conclusive we need results from running this test with the memory-cache turned off. | ||
We have run some tests with a slightly modified tp4m to better test cache performance. See [[Necko/MobileCache/Tp4m]] for more details. | |||
We need much more detailed information about what's going on. So we need to write and run some microbenchmarks that will test our current theories and quantify what (if any) performance cost they may have. For further details please visit [[Necko/MobileCache/MicroBenchmarks]]. | We need much more detailed information about what's going on. So we need to write and run some microbenchmarks that will test our current theories and quantify what (if any) performance cost they may have. For further details please visit [[Necko/MobileCache/MicroBenchmarks]]. | ||
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*What size disk caches do other mobile browsers use? | *What size disk caches do other mobile browsers use? | ||
**Android Browser - Appears to be 6MB according to the source code mirrored at https://github.com/android/platform_frameworks_base/blob/master/core/java/android/webkit/CacheManager.java#L60 | **Android Browser - Appears to be 6MB according to the source code mirrored at https://github.com/android/platform_frameworks_base/blob/master/core/java/android/webkit/CacheManager.java#L60 | ||
***On a rooted Froyo phone, you can see the cache is stored at /dbdata/databases/com.android.browser/cache/webviewCache. Experiments confirm the 6MB capacity. Each entry is stored as received from the network, in its own file (there are no block files). The maximum entry size is about 2MB (larger files are not stored). | |||
**Chrome Mobile (especially interesting given Chrome's similar disk cache implementation) - Can't find anything on this (yet), hopefully will get easier once ICS is released and we can (hopefully) see the config on a running mobile chrome. | **Chrome Mobile (especially interesting given Chrome's similar disk cache implementation) - Can't find anything on this (yet), hopefully will get easier once ICS is released and we can (hopefully) see the config on a running mobile chrome. | ||
**Opera Mobile (not the crappy "download pre-rendered pages" version) - 10000K according to opera:config (this is 1/2 what the desktop version has by default). Note that Opera also has a separate media cache which defaults to 10x the regular disk cache size. | **Opera Mobile (not the crappy "download pre-rendered pages" version) - 10000K according to opera:config (this is 1/2 what the desktop version has by default). Note that Opera also has a separate media cache which defaults to 10x the regular disk cache size. | ||