I've tracked down the problem to, I'm guessing, unsafe malloc in the lbry kernel.  Noticed that my mining rig, with only 2mb ram sees 25% memory use from ccminer -- pretty high.  When i drop caches the problem instantly goes away.  It doesn't, however, go away when I embed that drop_caches in the miner launch mechanism, so it's me fighting against some probabilistic processes.

Does that help narrow it down?  At a glance the only malloc I saw was cudaMalloc - does that malloc system memory?