Cache Notes

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ToDo List

Here are some things we can investigate to gain more information about the current state of the cache:

  • Determine what the cache's average hit rate is.
  • See how performance varies by increasing the cache size.
  • Look into whether YouTube files are blowing out the cache.
  • Run a Test Pilot or a smaller experiment to gather user cache data
    • In order to gather info on the previous bullet points

Here are some ideas for improving the cache that need to be investigated:

  • Consider other eviction options
    • Prioritize by file type, giving css and js higher priority
    • Evict based on "frecency", not just recency (frequency + recency)
    • Use Adaptive Replacement Cache algorithm:
    • We could consider letting servers specify "cache-priority" with resources. This leads to other issues, like fairness.
  • Keep dimensions of evicted image files, so layout can still render before the image data arrives across the network
  • Compress cache entries?
    • This could save space and improve I/O time
  • Don't throw away the entire cache when the browser crashes.

And here are some miscellaneous items:

  • Add more info to about:cache, including hit rates and other info.

List of Other Cache Resources

Here are some links with other documentation on the cache.

Here is a list of bugs filed on the cache. Many are resolved.

  • (http_cache) Meta-bug: improve HTTP cache bug 559729
  • Eliminate synchronous reads from cache (make cache reads asynchronous): bug 513008
  • Remove sync writes from current cache: bug 513074
  • Write/flush cache metadata off main-thread: bug 549767
  • xpcshell tests: assertion "mem cache leaking entries" in nsMemoryCacheDevice::Shutdown() causing abort test failed: bug 548406
  • Replace necko cache with the Google Chrome cache: bug 514213
  • Implement modern cache: bug 512849
  • Disk Cache overflow when downloading large files: bug 443067
  • Cache corruption when viewing sites with several large images (simultaneous hash collision & cache dooming by disk cache size limit): bug 321361
  • Increase default disk cache size: bug 193911
  • Figure out the max nr of entries we should store in the disk cache: bug 569709
  • Some files are never cached due to hash collisions which are quite common due to weak string hash function: bug 290032
  • Firefox stores corrupted version of cached JavaScript file (merges two files together): bug 355567
  • Need to teach necko to deal with channels reading and writing to a cache entry simultaniously: bug 446876