From c6c919eb90e021fbcfcbfa9dd3d55930cdbb67f9 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Tue, 26 Jul 2016 15:23:02 -0700 Subject: [PATCH] mm: use put_page() to free page instead of putback_lru_page() Recently, I got many reports about perfermance degradation in embedded system(Android mobile phone, webOS TV and so on) and easy fork fail. The problem was fragmentation caused by zram and GPU driver mainly. With memory pressure, their pages were spread out all of pageblock and it cannot be migrated with current compaction algorithm which supports only LRU pages. In the end, compaction cannot work well so reclaimer shrinks all of working set pages. It made system very slow and even to fail to fork easily which requires order-[2 or 3] allocations. Other pain point is that they cannot use CMA memory space so when OOM kill happens, I can see many free pages in CMA area, which is not memory efficient. In our product which has big CMA memory, it reclaims zones too exccessively to allocate GPU and zram page although there are lots of free space in CMA so system becomes very slow easily. To solve these problem, this patch tries to add facility to migrate non-lru pages via introducing new functions and page flags to help migration. struct address_space_operations { .. .. bool (*isolate_page)(struct page *, isolate_mode_t); void (*putback_page)(struct page *); .. } new page flags PG_movable PG_isolated For details, please read description in "mm: migrate: support non-lru movable page migration". Originally, Gioh Kim had tried to support this feature but he moved so I took over the work. I took many code from his work and changed a little bit and Konstantin Khlebnikov helped Gioh a lot so he should deserve to have many credit, too. And I should mention Chulmin who have tested this patchset heavily so I can find many bugs from him. :) Thanks, Gioh, Konstantin and Chulmin! This patchset consists of five parts. 1. clean up migration mm: use put_page to free page instead of putback_lru_page 2. add non-lru page migration feature mm: migrate: support non-lru movable page migration 3. rework KVM memory-ballooning mm: balloon: use general non-lru movable page feature 4. zsmalloc refactoring for preparing page migration zsmalloc: keep max_object in size_class zsmalloc: use bit_spin_lock zsmalloc: use accessor zsmalloc: factor page chain functionality out zsmalloc: introduce zspage structure zsmalloc: separate free_zspage from putback_zspage zsmalloc: use freeobj for index 5. zsmalloc page migration zsmalloc: page migration support zram: use __GFP_MOVABLE for memory allocation This patch (of 12): Procedure of page migration is as follows: First of all, it should isolate a page from LRU and try to migrate the page. If it is successful, it releases the page for freeing. Otherwise, it should put the page back to LRU list. For LRU pages, we have used putback_lru_page for both freeing and putback to LRU list. It's okay because put_page is aware of LRU list so if it releases last refcount of the page, it removes the page from LRU list. However, It makes unnecessary operations (e.g., lru_cache_add, pagevec and flags operations. It would be not significant but no worth to do) and harder to support new non-lru page migration because put_page isn't aware of non-lru page's data structure. To solve the problem, we can add new hook in put_page with PageMovable flags check but it can increase overhead in hot path and needs new locking scheme to stabilize the flag check with put_page. So, this patch cleans it up to divide two semantic(ie, put and putback). If migration is successful, use put_page instead of putback_lru_page and use putback_lru_page only on failure. That makes code more readable and doesn't add overhead in put_page. Comment from Vlastimil "Yeah, and compaction (perhaps also other migration users) has to drain the lru pvec... Getting rid of this stuff is worth even by itself." Link: http://lkml.kernel.org/r/1464736881-24886-2-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim Acked-by: Vlastimil Babka Cc: Rik van Riel Cc: Mel Gorman Cc: Hugh Dickins Cc: Naoya Horiguchi Cc: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/migrate.c | 68 ++++++++++++++++++++++++++++++++-------------------- 1 file changed, 42 insertions(+), 26 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index bd3fdc202e8b..c74412b381ff 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -915,6 +915,19 @@ out_unlock: put_anon_vma(anon_vma); unlock_page(page); out: + /* + * If migration is successful, decrease refcount of the newpage + * which will not free the page because new page owner increased + * refcounter. As well, if it is LRU page, add the page to LRU + * list in here. + */ + if (rc == MIGRATEPAGE_SUCCESS) { + if (unlikely(__is_movable_balloon_page(newpage))) + put_page(newpage); + else + putback_lru_page(newpage); + } + return rc; } @@ -948,6 +961,12 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, if (page_count(page) == 1) { /* page was freed from under us. So we are done. */ + ClearPageActive(page); + ClearPageUnevictable(page); + if (put_new_page) + put_new_page(newpage, private); + else + put_page(newpage); goto out; } @@ -960,10 +979,8 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, } rc = __unmap_and_move(page, newpage, force, mode); - if (rc == MIGRATEPAGE_SUCCESS) { - put_new_page = NULL; + if (rc == MIGRATEPAGE_SUCCESS) set_page_owner_migrate_reason(newpage, reason); - } out: if (rc != -EAGAIN) { @@ -976,33 +993,32 @@ out: list_del(&page->lru); dec_zone_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); - /* Soft-offlined page shouldn't go through lru cache list */ - if (reason == MR_MEMORY_FAILURE && rc == MIGRATEPAGE_SUCCESS) { - /* - * With this release, we free successfully migrated - * page and set PG_HWPoison on just freed page - * intentionally. Although it's rather weird, it's how - * HWPoison flag works at the moment. - */ - put_page(page); - if (!test_set_page_hwpoison(page)) - num_poisoned_pages_inc(); - } else - putback_lru_page(page); } /* - * If migration was not successful and there's a freeing callback, use - * it. Otherwise, putback_lru_page() will drop the reference grabbed - * during isolation. + * If migration is successful, releases reference grabbed during + * isolation. Otherwise, restore the page to right list unless + * we want to retry. */ - if (put_new_page) - put_new_page(newpage, private); - else if (unlikely(__is_movable_balloon_page(newpage))) { - /* drop our reference, page already in the balloon */ - put_page(newpage); - } else - putback_lru_page(newpage); + if (rc == MIGRATEPAGE_SUCCESS) { + put_page(page); + if (reason == MR_MEMORY_FAILURE) { + /* + * Set PG_HWPoison on just freed page + * intentionally. Although it's rather weird, + * it's how HWPoison flag works at the moment. + */ + if (!test_set_page_hwpoison(page)) + num_poisoned_pages_inc(); + } + } else { + if (rc != -EAGAIN) + putback_lru_page(page); + if (put_new_page) + put_new_page(newpage, private); + else + put_page(newpage); + } if (result) { if (rc)