This patch adds a write optimizer to LSSnapshot. The optimizer is only used when
there are no observers for other content processes.
Differential Revision: https://phabricator.services.mozilla.com/D31199
This patch renames the Checkpoint IPC message to CheckpointAndNotify. Other structures used by checkpointing are renamed too. Datastore methods SetItem/RemoveItem/Clear no longer call NotifyObservers, it's now up to RecvCheckpointAndNotify to call it.
Differential Revision: https://phabricator.services.mozilla.com/D31197
This improves performance by keeping snapshots around for some time if there are no changes done by other processes. If a snapshot is not destroyed immediately after getting into the stable state then there's a chance that it won't have to be synchronously created again when a new opeartion is requested.
There's now an upper limit for snapshot prefilling. The value is configurable and is currently set to 4096 bytes.
Snapshots can operate in multiple modes depending on if all items have been loaded or all keys have been received. This should provide the best performance for each specific state.
This patch also adds support for creating explicit snapshots which can be used for testing.
This improves performance a lot in cases when multiple operations are invoked by a single JS function (number of sync IPC calls is reduced to a minimum). It also improves correctness since changes are not visible to other content processes until a JS function finishes.
The patch implements core infrastructure, all items are sent to content when a snapshot is initialized and everything is fully working. However, sending of all items at once is not optimal for bigger databases. Support for lazy loading of items is implemented in a following patch.