On Tue, Oct 18, 2016 at 06:55:12PM +0530, Goel, Akash wrote: > > > On 10/18/2016 5:35 PM, Joonas Lahtinen wrote: > >On ma, 2016-04-04 at 14:18 +0100, Chris Wilson wrote: > >>From: Akash Goel <akash.goel@xxxxxxxxx> > >> > >>On a long run of more than 2-3 days, physical memory tends to get > >>fragmented severely, which considerably slows down the system. In such a > >>scenario, the shrinker is also unable to help as lack of memory is not > >>the actual problem, since it has been observed that there are enough free > >>pages of 0 order. This also manifests itself when an indiviual zone in > >>the mm runs out of pages and if we cannot migrate pages between zones, > >>the kernel hits an out-of-memory even though there are free pages (and > >>often all of swap) available. > >> > >>To address the issue of external fragementation, kernel does a compaction > >>(which involves migration of pages) but it's efficacy depends upon how > >>many pages are marked as MOVABLE, as only those pages can be migrated. > >> > >>Currently the backing pages for GFX buffers are allocated from shmemfs > >>with GFP_RECLAIMABLE flag, in units of 4KB pages. In the case of limited > >>swap space, it may not be possible always to reclaim or swap-out pages of > >>all the inactive objects, to make way for free space allowing formation > >>of higher order groups of physically-contiguous pages on compaction. > >> > >>Just marking the GPU pages as MOVABLE will not suffice, as i915.ko has to > >>pin the pages if they are in use by GPU, which will prevent their > >>migration. So the migratepage callback in shmem is also hooked up to get > >>a notification when kernel initiates the page migration. On the > >>notification, i915.ko appropriately unpin the pages. With this we can > >>effectively mark the GPU pages as MOVABLE and hence mitigate the > >>fragmentation problem. > >> > >>v2: > >> - Rename the migration routine to gem_shrink_migratepage, move it to the > >> shrinker file, and use the existing constructs (Chris) > >> - To cleanup, add a new helper function to encapsulate all page migration > >> skip conditions (Chris) > >> - Add a new local helper function in shrinker file, for dropping the > >> backing pages, and call the same from gem_shrink() also (Chris) > >> > >>v3: > >> - Fix/invert the check on the return value of unsafe_drop_pages (Chris) > >> > >>v4: > >> - Minor tidy > >> > >>Testcase: igt/gem_shrink > >>Bugzilla: (e.g.) https://bugs.freedesktop.org/show_bug.cgi?id=90254 > >>Cc: Hugh Dickins <hughd@xxxxxxxxxx> > >>Cc: linux-mm@xxxxxxxxx > >>Signed-off-by: Sourab Gupta <sourab.gupta@xxxxxxxxx> > >>Signed-off-by: Akash Goel <akash.goel@xxxxxxxxx> > >>Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > > >Could this patch be re-spinned on top of current nightly? > > > Sure will rebase it on top of nightly. It's in my tree (on top of nightly) already with Joonas' r-b. -Chris -- Chris Wilson, Intel Open Source Technology Centre -- 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>