Bob Dorr talks about a trace flag:
SQL Server optimizes database log file flush requests, performing these flush requests inline on the active worker. Certain patterns of log record activity may encounter increased spinlock contention while performing the log cache block flush activities.
Trace flag -T8904 (startup only trace flag) disables inline log flush, limiting the contention possibility from many workers to the subset of background LogWriter workers. When the trace flag is enabled, the worker adding log records mark the log cache block to be flushed and a background LogWriter worker performs the flush activity.
Read on to learn more, including a call-out to Curated SQL favorite Lonny Niederstadt.