Another feature has been added to Snappy project of Mozilla to optimize startup performance of Firefox- Mozilla has landed a patch on Firefox 15 nightly to clear Firefox PF files in Windows Prefetch folder on its shutdown. Here Firefox on first startup prompts the service to check for Firefox PF files in Prefetch folder that are not o KB and sets them to o KB Firefox PF files read-only. Once these files set as read-only they can’t be re-created by Windows. When the prefetch process is over the about:config preference value of "app.update.service.prefetchCleared" will be set to “true”. This clearing prefetch happens only once for first startup after 1 minute or during Firefox update from version that has not supported on.
Prefetch delays “First Paint” of Firefox, tests performed by Mozilla shows that with no Prefetch Firefox takes less time to start than with Prefetch enabled. With this feature Firefox will monitor the Prefetch directory for non-zero KB PF files of Firefox and clears them and sets them to o KB read-only files. For each install and each upgrade of Firefox this prefetch process will run. When the Prefetch process is over, faster startup occurs on the next or second startup.