On Wed, 08 Jul 2015 09:02:59 +0900 Gioh Kim <gioh.kim@xxxxxxx> wrote: > > > 2015-07-08 ______ 7:37___ Andrew Morton ___(___) ___ ___: > > On Tue, 7 Jul 2015 13:36:20 +0900 Gioh Kim <gioh.kim@xxxxxxx> wrote: > > > >> From: Gioh Kim <gurugio@xxxxxxxxxxx> > >> > >> 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. > >> > >> ... > >> > >> This patch set is tested: > >> - 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 > > > > OK, but what happens if the balloon driver is not used to force > > compaction? Does your test machine successfully compact pages on > > demand, so those order-3 allocations now succeed? > > If any driver that has many pages like the balloon driver is forced to compact, > the system can get free high-order pages. > > I have to show how this patch work with a driver existing in the kernel source, > for kernel developers' undestanding. So I selected the balloon driver > because it has already compaction and working with kernel compaction. > I can show how driver pages is compacted with lru-pages together. > > Actually balloon driver is not best example to show how this patch compacts pages. > The balloon driver compaction is decreasing page consumtion, for instance 1024MB -> 512MB. > I think it is not compaction precisely. It frees pages. > Of course there will be many high-order pages after 512MB is freed. Can the various in-kernel GPU drivers benefit from this? If so, wiring up one or more of those would be helpful? -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
