- * yield and let another thread piggyback onto this transaction.
- * Keep doing that while new threads continue to arrive.
- * It doesn't cost much - we're about to run a commit and sleep
- * on IO anyway. Speeds up many-threaded, many-dir operations
- * by 30x or more...
+ * yield and let another thread piggyback onto this
+ * transaction. Keep doing that while new threads continue to
+ * arrive. It doesn't cost much - we're about to run a commit
+ * and sleep on IO anyway. Speeds up many-threaded, many-dir
+ * operations by 30x or more...
+ *
+ * We try and optimize the sleep time against what the
+ * underlying disk can do, instead of having a static sleep
+ * time. This is useful for the case where our storage is so
+ * fast that it is more optimal to go ahead and force a flush
+ * and wait for the transaction to be committed than it is to
+ * wait for an arbitrary amount of time for new writers to
+ * join the transaction. We achieve this by measuring how
+ * long it takes to commit a transaction, and compare it with
+ * how long this transaction has been running, and if run time
+ * < commit time then we sleep for the delta and commit. This
+ * greatly helps super fast disks that would see slowdowns as
+ * more threads started doing fsyncs.