Hello, RFC Posting as an early preview of zsmalloc compaction and density improvements. The patch set will be rebased once Minchan posts his zsmalloc rework. zsmalloc knows the watermark after which classes are considered to be huge - every object stored consumes the entire zspage (which consist of a single order-0 page). zram, however, has its own statically defined watermark for `bad' compression and stores every object larger than this watermark as a PAGE_SIZE, object, IOW, to a ->huge class, this results in increased memory consumption and memory wastage. And zram's 'bad' watermark is much lower than zsmalloc's one. Apart from that, 'bad' compressions are not so rare and expecting that pages passed to zram mostly will be compressed to 3/4 of page_size is a bit strange. There is no a compression algorithm with such ratio guarantees. This patch set inverts this 'huge class watermark' enforcement, it's zsmalloc that knows better, not zram. The patch set reduces the number of huge classes, which permits to save some memory. zsmalloc classes are known to have fragmentation problems, that's why compaction has been aidded in the first place. The patch set change the existing shrinker callback based compaction and introduces a watermark based one. So now zsmalloc controls class's fragmentation level and schedules a compaction work on a per-class basis once class fragmentation jumps above the watermark. Instead of compacting the entire pool class-by-class we know touch only classes that are known to be heavily fragmented. All important patches contain test results and test descriptions. And it seems that previously weak tests (truncate) are no longer problematic. v3: -- user watermark based per-class compaction (workqueue) -- remove shrinker compaction callbacks -- increase order only for huge classes via special #defines -- renamed zs_get_huge_class_size_watermark() function -- patches re-ordered v2: -- keep ZS_MAX_PAGES_PER_ZSPAGE order of two (Joonsoo) -- suffice ZS_MIN_ALLOC_SIZE alignment requirement -- do not change ZS_MAX_PAGES_PER_ZSPAGE on PAE/LPAE and on PAGE_SHIFT 16 systems (Joonsoo) Sergey Senozhatsky (5): mm/zsmalloc: introduce class auto-compaction mm/zsmalloc: remove shrinker compaction callbacks mm/zsmalloc: introduce zs_huge_object() zram: use zs_huge_object() mm/zsmalloc: reduce the number of huge classes drivers/block/zram/zram_drv.c | 2 +- drivers/block/zram/zram_drv.h | 6 -- include/linux/zsmalloc.h | 2 + mm/zsmalloc.c | 157 ++++++++++++++++++++---------------------- 4 files changed, 78 insertions(+), 89 deletions(-) -- 2.8.0.rc0 -- 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>