• Marcelo Ricardo Leitner's avatar
    sctp: introduce priority based stream scheduler · 637784ad
    Marcelo Ricardo Leitner authored
    This patch introduces RFC Draft ndata section 3.4 Priority Based
    Scheduler (SCTP_SS_PRIO).
    
    It works by having a struct sctp_stream_priority for each priority
    configured. This struct is then enlisted on a queue ordered per priority
    if, and only if, there is a stream with data queued, so that dequeueing
    is very straightforward: either finish current datamsg or simply dequeue
    from the highest priority queued, which is the next stream pointed, and
    that's it.
    
    If there are multiple streams assigned with the same priority and with
    data queued, it will do round robin amongst them while respecting
    datamsgs boundaries (when not using idata chunks), to be reasonably
    fair.
    
    We intentionally don't maintain a list of priorities nor a list of all
    streams with the same priority to save memory. The first would mean at
    least 2 other pointers per priority (which, for 1000 priorities, that
    can mean 16kB) and the second would also mean 2 other pointers but per
    stream. As SCTP supports up to 65535 streams on a given asoc, that's
    1MB. This impacts when giving a priority to some stream, as we have to
    find out if the new priority is already being used and if we can free
    the old one, and also when tearing down.
    
    The new fields in struct sctp_stream_out_ext and sctp_stream are added
    under a union because that memory is to be shared with other schedulers.
    
    See-also: https://tools.ietf.org/html/draft-ietf-tsvwg-sctp-ndata-13Tested-by: default avatarXin Long <lucien.xin@gmail.com>
    Signed-off-by: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    637784ad
stream_sched.c 6.32 KB