Perforce add capability to do parallel sync, see:
 --parallel


Specify options for parallel file transfer. The configuration variable net.parallel.max must be set to a value greater than 1 to enable the --parallel option.

    threads=n sends files concurrently using n independent network connections. The specified threads grab work in batches.

    batch=n specifies the number of files in a batch.

    batchsize=n specifies the number of bytes in a batch.

    min=n specifies the minimum number of files in a parallel sync. A sync that is too small will not initiate parallel file transfers.

    minsize=n specifies the minimum number of bytes in a parallel sync. A sync that is too small will not initiate parallel file transfers.

More info: http://www.perforce.com/perforce/doc.current/manuals/cmdref/p4_sync.html#p4_sync.usage.parallel