On Fri 01-08-14 10:06:40, Gioh Kim wrote: > Function path is like followings: > > [ 97.868304] [<8011a750>] (drop_buffers+0xfc/0x168) from [<8011bc64>] (try_to_free_buffers+0x50/0xbc) > [ 97.877457] [<8011bc64>] (try_to_free_buffers+0x50/0xbc) from [<80121e40>] (blkdev_releasepage+0x38/0x48) > [ 97.887093] [<80121e40>] (blkdev_releasepage+0x38/0x48) from [<800add8c>] (try_to_release_page+0x40/0x5c) > [ 97.896728] [<800add8c>] (try_to_release_page+0x40/0x5c) from [<800bd9bc>] (shrink_page_list+0x508/0x8a4) > [ 97.906334] [<800bd9bc>] (shrink_page_list+0x508/0x8a4) from [<800bde5c>] (reclaim_clean_pages_from_list+0x104/0x148) > [ 97.917017] [<800bde5c>] (reclaim_clean_pages_from_list+0x104/0x148) from [<800b5dec>] (alloc_contig_range+0x114/0x2dc) > [ 97.927856] [<800b5dec>] (alloc_contig_range+0x114/0x2dc) from [<802f6c04>] (dma_alloc_from_contiguous+0x8c/0x14c) > [ 97.938264] [<802f6c04>] (dma_alloc_from_contiguous+0x8c/0x14c) from [<80017b6c>] (__alloc_from_contiguous+0x34/0xc0) > [ 97.948926] [<80017b6c>] (__alloc_from_contiguous+0x34/0xc0) from [<80017d40>] (__dma_alloc+0xc4/0x2a0) > [ 97.958362] [<80017d40>] (__dma_alloc+0xc4/0x2a0) from [<8001803c>] (arm_dma_alloc+0x80/0x98) > [ 97.966916] [<8001803c>] (arm_dma_alloc+0x80/0x98) from [<7f6ea188>] (cma_test_probe+0xe0/0x1f0 [drv]) OK, this makes more sense to me. But also as Joonsoo Kim pointed out even if we go into the migration path, we will end up calling try_to_free_buffers() because blkdev pages are one of those which use fallback_migrate_page() as their ->migratepage callback. Now regarding your quest to make all pages in the movable zone really movable - you are going to have hard time to achieve that for blkdev pages. E.g. when a metadata buffer is part of a running transaction, it will be pinned in memory until that transaction commits which easily takes seconds. And for busy metadata buffer there's no guarantee that after that transaction commits the buffer isn't already part of the newly started transaction. So these buffers may be effectively unmovable while someone writes to the filesystem. So the quiestion really is how hard guarantee do you need that a page in movable zone is really movable. Or better in what timeframe should it be movable? It may be possible to make e.g. migratepage callback for ext4 blkdev pages which will handle migration of pages that are just idly sitting in a journal waiting to be committed. That may be reasonably doable although it won't be perfect. Or we may just decide it's not worth the bother and allocate all blkdev pages from unmovable zone... Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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>