On Fri, Jun 05, 2015 at 11:35:49PM +0900, Gioh Kim wrote: > >On Tue, Jun 02, 2015 at 04:27:40PM +0900, Gioh Kim wrote: > >>Hello, > >> > >>This series try to enable migration of non-LRU pages, such as driver's page. > >> > >>My ARM-based platform occured severe fragmentation problem after long-term > >>(several days) test. Sometimes even order-3 page allocation failed. It has > >>memory size 512MB ~ 1024MB. 30% ~ 40% memory is consumed for graphic processing > >>and 20~30 memory is reserved for zram. > >> > >>I found that many pages of GPU driver and zram are non-movable pages. So I > >>reported Minchan Kim, the maintainer of zram, and he made the internal > >>compaction logic of zram. And I made the internal compaction of GPU driver. > >> > >>They reduced some fragmentation but they are not enough effective. > >>They are activated by its own interface, /sys, so they are not cooperative > >>with kernel compaction. If there is too much fragmentation and kernel starts > >>to compaction, zram and GPU driver cannot work with the kernel compaction. > >> > >>The first this patch adds a generic isolate/migrate/putback callbacks for page > >>address-space. The zram and GPU, and any other modules can register > >>its own migration method. The kernel compaction can call the registered > >>migration when it works. Therefore all page in the system can be migrated > >>at once. > >> > >>The 2nd the generic migration callbacks are applied into balloon driver. > >>My gpu driver code is not open so I apply generic migration into balloon > >>to show how it works. I've tested it with qemu enabled by kvm like followings: > >>- turn on Ubuntu 14.04 with 1G memory on qemu. > >>- do kernel building > >>- after several seconds check more than 512MB is used with free command > >>- command "balloon 512" in qemu monitor > >>- check hundreds MB of pages are migrated > >> > >>Next kernel compaction code can call generic migration callbacks instead of > >>balloon driver interface. > >>Finally calling migration of balloon driver is removed. > >> > > > >In a glance, ss Konstantin pointed out this set, while it twists chunks around, > >brings back code we got rid of a while ago because it was messy and racy. > > Yes, your point is right. > > >I'll take a closer look into your work next week, but for now, I'd say > >we should not follow this patch of reintroducing long-dead code. > > BUT as I replied to Konstantin, the code for balloon driver is to show > how the generic callbacks can be applied. > > My point is there are some pages to be migrated which are not LRU pages, > but there is no interface for them to migrate. > > For example gpu driver has many, not mapped to kernel space, pages. > Those pages can be migrated when GPU is not working, screen is not refreshed. > And zram pages can be migrated also. > > I'm very sorry that I'm not familiar to balloon driver. > If you give me some hints, I might be able to refine code of patch 2~3 in the next spin. > NP at all. Thanks for bringing this discussion of migrating non-LRU pages back to the table, actually. As I mentioned earlier, I'll take a closer look into your work as soon as I get time next week, so I can try to help with more qualified feedback. Have a nice weekend! -- Rafael -- 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>