There’s been a project that’s been going on for several years to move Firefox’s bookmarks processing off the main thread and to happen in the background – to help reduce possible jerkiness when dealing with bookmarks.
One part of this (Places Transactions) has been enabled in Nightly for about 4-5 weeks. We think we’ve fixed all the regressions for this, and we’d now like more people testing.
So, when you’re checking out the improved performance of Firefox Nightly, please also keep an eye on Bookmarks – if you’re moving/copying/editing them, and you undo/redo actions, check that everything behaves as it should.
If it doesn’t, please file a bug with how to reproduce and we’ll take a look. If you can also test with the preference browser.places.useAsyncTransactions set to false (after a restart) to know if it happens with the old style transactions – that will help us finding the issue.
We know there’s still some performance issues with the new async transactions which we’re currently working on and hope to be landing fixes for those soon.