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Date: Fri, 30 Aug 2013 10:42:52 +0200 From: Krzysztof Kozlowski <k.kozlowski@...sung.com> To: Seth Jennings <sjenning@...ux.vnet.ibm.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org> Cc: Bob Liu <bob.liu@...cle.com>, Mel Gorman <mgorman@...e.de>, Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>, Marek Szyprowski <m.szyprowski@...sung.com>, Kyungmin Park <kyungmin.park@...sung.com>, Dave Hansen <dave.hansen@...el.com>, Minchan Kim <minchan@...nel.org>, Krzysztof Kozlowski <k.kozlowski@...sung.com> Subject: [RFC PATCH 0/4] mm: migrate zbud pages Hi, Currently zbud pages are not movable and they cannot be allocated from CMA region. These patches add migration of zbud pages. The zbud migration code utilizes mapping so many exceptions to migrate code was added. It can be replaced for example with pin page control subsystem: http://article.gmane.org/gmane.linux.kernel.mm/105308 In such case the zbud migration code (zbud_migrate_page()) can be safely re-used. Patch "[PATCH 3/4] mm: use indirect zbud handle and radix tree" changes zbud handle to support migration. Now the handle is an index in radix tree and zbud_map() maps it to proper virtual address. This exposes race conditions, some of them are discussed already here: http://article.gmane.org/gmane.linux.kernel.mm/105988 Races are fixed by adding internal map count for each zbud handle. The map count is increased on zbud_map() call. Some races between writeback and invalidate still exist. In such case a message can be seen in logs: zbud: error: could not lookup handle 13810 in tree Patches from discussion above may resolve it. I have considered using "pgoff_t offset" as handle but it prevented storing duplicate pages in zswap. Patch "[PATCH 2/4] mm: use mapcount for identifying zbud pages" introduces PageZbud() function which identifies zbud pages by page->_mapcount. Dave Hansen proposed aliasing PG_zbud=PG_slab but in such case patch would be more intrusive. Any ideas for a better solution are welcome. This patch set is based on v3.11-rc7-30-g41615e8. This is continuation of my previous work: reclaiming zbud pages on migration and compaction. However it current solution is completely different so I am not attaching previous changelog. Previous patches can be found here: * [RFC PATCH v2 0/4] mm: reclaim zbud pages on migration and compaction http://article.gmane.org/gmane.linux.kernel.mm/105153 * [RFC PATCH 0/4] mm: reclaim zbud pages on migration and compaction http://article.gmane.org/gmane.linux.kernel.mm/104801 One patch from previous work is re-used along with minor changes: "[PATCH 1/4] zbud: use page ref counter for zbud pages" * Add missing spin_unlock in zbud_reclaim_page(). * Decrease pool->pages_nr in zbud_free(), not when putting page. This also removes the need of holding lock while call to put_zbud_page(). Best regards, Krzysztof Kozlowski Krzysztof Kozlowski (4): zbud: use page ref counter for zbud pages mm: use mapcount for identifying zbud pages mm: use indirect zbud handle and radix tree mm: migrate zbud pages include/linux/mm.h | 23 +++ include/linux/zbud.h | 3 +- mm/compaction.c | 7 + mm/migrate.c | 17 +- mm/zbud.c | 552 +++++++++++++++++++++++++++++++++++++++++--------- mm/zswap.c | 28 ++- 6 files changed, 525 insertions(+), 105 deletions(-) -- 1.7.9.5 -- 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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