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