On Thu, 9 May 2013 16:21:22 +0900 Minchan Kim <minc...@kernel.org> wrote:
> These day, there are many platforms avaiable in the embedded market > and they are smarter than kernel which has very limited information > about working set so they want to involve memory management more heavily > like android's lowmemory killer and ashmem or recent many lowmemory > notifier(there was several trial for various company NOKIA, SAMSUNG, > Linaro, Google ChromeOS, Redhat). > > One of the simple imagine scenario about userspace's intelligence is that > platform can manage tasks as forground and backgroud so it would be > better to reclaim background's task pages for end-user's *responsibility* > although it has frequent referenced pages. > > The patch[1] prepares that force_reclaim in shrink_page_list can > handle anonymous pages as well as file-backed pages. > > The patch[2] adds new knob "reclaim under proc/<pid>/" so task manager > can reclaim any target process anytime, anywhere. It could give another > method to platform for using memory efficiently. > > It can avoid process killing for getting free memory, which was really > terrible experience because I lost my best score of game I had ever > after I switch the phone call while I enjoyed the game. > > Reclaim file-backed pages only. > echo file > /proc/PID/reclaim > Reclaim anonymous pages only. > echo anon > /proc/PID/reclaim > Reclaim all pages > echo all > /proc/PID/reclaim Oh boy. I think I do agree with the overall intent, but there are so many ways of doing this. - Do we reclaim the pages altogether, or should we just give them one round of aging? If the latter then you'd need to run "echo anon > /proc/PID/reclaim" four times to firmly whack the pages, but that's more flexible. - Why do it via the pid at all? Would it be better to instead do this to a memcg and require that the admin put these processes into memcgs? In fact existing memcg controls could get us at least partway to this feature. - I don't understand the need for "Enhance per process reclaim to consider shared pages". If "echo file > /proc/PID/reclaim" causes PID's mm's file-backed pte's to be unmapped (which seems to be the correct effect) then we get this automatically: unshared file pages will be freed and shared file pages will remain in core until the other sharing process's also unmap them. Overall, I'm unsure whether/how to proceed with this. I'd like to hear from a lot of the potential users, and hear them say "yes, we can use this". -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
