just recently noticed some post with complaints about both netflow delays/jitter and multicast issues, compared to SOHO routers.
and in few articles in web folks concludes thats impact of bloadbuffer in ancient linux cores, used in actual ROS builds.
so to mildly mitigate issues they suggest, which is quite unexpecting to put in into “inteface queues” for ethernet ports(and most issues/reporta was about) instead “only-hardware-queue” something different, like “default” or create manually random pffifo queue type with buffer lenght from 10 to 60 packets(play with for better effects).
its should sounds funny, but works on my 751, 951, 450g and 2011 devices(not tried on working stuff, only personal property).
so may be if you configuration not depend on fast-path much, if would helps you. personally i was found 100packets buffer even more suitable for 951g and rb2011ui, but thats depend of hardware/traffic combiantion, i suppose.
p.s.
i guess MT changed ethernet defaults in ROS shortly before fast-path introduction for MIPS-BE devices.
ie long ago.