Dovecot 2.3+ mailbox_list_index: concurrent write serialization bottleneck
Context Since Dovecot 2.3 the mailbox_list_index feature is enabled by default, maintaining a per-user index ( dovecot.list.index plus .log ) that accelerates LIST and LSUB commands. The index is updated under an exclusive fcntl / flock lock for every mailbox write operation (EXPUNGE, MOVE, COPY, etc.). Constraint The design chooses strict consistency over t
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