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Date: Wed, 08 Jul 2015 09:02:59 +0900 From: Gioh Kim <gioh.kim@....com> To: Andrew Morton <akpm@...ux-foundation.org> CC: jlayton@...chiereds.net, bfields@...ldses.org, vbabka@...e.cz, iamjoonsoo.kim@....com, viro@...iv.linux.org.uk, mst@...hat.com, koct9i@...il.com, minchan@...nel.org, aquini@...hat.com, linux-fsdevel@...r.kernel.org, virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org, linux-api@...r.kernel.org, linux-mm@...ck.org, gunho.lee@....com, Gioh Kim <gurugio@...mail.net> Subject: Re: [RFCv3 0/5] enable migration of driver pages 2015-07-08 오전 7:37에 Andrew Morton 이(가) 쓴 글: > On Tue, 7 Jul 2015 13:36:20 +0900 Gioh Kim <gioh.kim@....com> wrote: > >> From: Gioh Kim <gurugio@...mail.net> >> >> 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. > > Why are your changes to the GPU driver not included in this patch series? My platform is ARM-based and GPU is ARM-Mali. The driver is not open source. It's too bad that I cannot show effect of this patch with the GPU driver. > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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