On Thu 04-05-17 17:49:21, Benjamin Herrenschmidt wrote: > On Thu, 2017-05-04 at 14:52 +0200, Michal Hocko wrote: > > But the direct reclaim would be effective only _after_ all other nodes > > are full. > > > > I thought that kswapd reclaim is a problem because the HW doesn't > > support aging properly but as the direct reclaim works then what is the > > actual problem? > > Ageing isn't isn't completely broken. The ATS MMU supports > dirty/accessed just fine. > > However the TLB invalidations are quite expensive with a GPU so too > much harvesting is detrimental, and the GPU tends to check pages out > using a special "read with intend to write" mode, which means it almost > always set the dirty bit if the page is writable to begin with. This sounds pretty much like a HW specific details which is not the right criterion to design general CDM around. So let me repeat the fundamental question. Is the only difference from cpuless nodes the fact that the node should be invisible to processes unless they specify an explicit node mask? If yes then we are talking about policy in the kernel and that sounds like a big no-no to me. Moreover cpusets already support exclusive numa nodes AFAIR. I am either missing something important here, and the discussion so far hasn't helped to be honest, or this whole CDM effort tries to build a generic interface around a _specific_ piece of HW. The matter is worse by the fact that the described usecases are so vague that it is hard to build a good picture whether this is generic enough that a new/different HW will still fit into this picture. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
