FWIW, I'm also confused about where the IO is in this profile. It looks like the time filters from comment #3 exclude the `clear()` call and its effects, but I'm not sure what else they exclude - basically I'm skeptical that fetching 1mb of json data over the network / from disk, and writing that to the indexeddb is 0-cost on the main thread besides the JS we use to process it.
Bug 1508332 Comment 5 Edit History
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FWIW, I'm also confused about where the IO is in this profile. It looks like the time filters from comment #3 exclude the `clear()` call and its effects, but I'm not sure what else they exclude - basically I'm skeptical that fetching 1mb of json data over the network / from disk, and writing that to the indexeddb is 0-cost on the main thread besides the JS we use to process it - I'd expect to see the JSON parsing, at a minimum.