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Wed, 19 Jun 2024 20:54:38 +0800 (CST) From: yangge1116@126.com To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, 21cnbao@gmail.com, baolin.wang@linux.alibaba.com, mgorman@techsingularity.net, liuzixing@hygon.cn, yangge Subject: [PATCH] mm/page_alloc: add one PCP list for THP Date: Wed, 19 Jun 2024 20:54:32 +0800 Message-Id: <1718801672-30152-1-git-send-email-yangge1116@126.com> X-Mailer: git-send-email 2.7.4 X-CM-TRANSID: _____wCnd28K1XJmBrxyBQ--.10118S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxAFWUtF17Xw18JF1UuFWDXFb_yoWrAr18pF WxJr4ayayjqryYyr1xA3Wqkr1rCwnxGFsrCrW8ury8ZwsxJFyS9a4UK3WqvF95ArW7AF48 XryDt34fCF4DZ3DanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07UfhL5UUUUU= X-Originating-IP: [118.242.3.34] X-CM-SenderInfo: 51dqwwjhrrila6rslhhfrp/1tbiOg8DG2VEw410VQAAsj X-Stat-Signature: fe8kg8oone6kb6n5wtg456accgxtb34h X-Rspamd-Queue-Id: 1162D140004 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1718801684-587784 X-HE-Meta: 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 lGbxlRzh oAGLFOteUfr07cP5d7LuG6e5gZ5s3QhKOZTRyq1b8qczd93fyApFLpK5SnygiCaZUQJiBdAu9+tsj0q3UV/4fpqazGhzGZN6286sdKZKNMBmFsCwhi3SfSbaXarwX4biInzhfSl2JrOra8eVsfQ8C5aUoK+Fox+cbnIZnQtZUmXu/3CRV7LFIQK2Mb2XFpLPly+17nh1BsIPNnKKuLqNaxTcK91ZsiroHJDJe6RsRFXvxRW0MnisJfDyLEhW/LjGcSXjdXdQp0lWlrczzHRkMC+bsNgmTOcFr/BRsRtw9QEAFvFb+wLjBHf4Iy5G4RSPfAF2UajsbKFFUxlsoF9HAXiSGfhiFWVcz5H2S9fF2KcP74jmkyFvG0VmrbmDEJ9BkSKE2DCWkxQIJ5z0H22ed6ZxTRtrW2KpotxeYNO29Cd8A3mQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: yangge Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") no longer differentiates the migration type of pages in THP-sized PCP list, it's possible that non-movable allocation requests may get a CMA page from the list, in some cases, it's not acceptable. If a large number of CMA memory are configured in system (for example, the CMA memory accounts for 50% of the system memory), starting a virtual machine with device passthrough will get stuck. During starting the virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM, ...) to pin memory. Normally if a page is present and in CMA area, pin_user_pages_remote() will migrate the page from CMA area to non-CMA area because of FOLL_LONGTERM flag. But if non-movable allocation requests return CMA memory, migrate_longterm_unpinnable_pages() will migrate a CMA page to another CMA page, which will fail to pass the check in check_and_migrate_movable_pages() and cause migration endless. Call trace: pin_user_pages_remote --__gup_longterm_locked // endless loops in this function ----_get_user_pages_locked ----check_and_migrate_movable_pages ------migrate_longterm_unpinnable_pages --------alloc_migration_target This problem will also have a negative impact on CMA itself. For example, when CMA is borrowed by THP, and we need to reclaim it through cma_alloc() or dma_alloc_coherent(), we must move those pages out to ensure CMA's users can retrieve that contigous memory. Currently, CMA's memory is occupied by non-movable pages, meaning we can't relocate them. As a result, cma_alloc() is more likely to fail. To fix the problem above, we add one PCP list for THP, which will not introduce a new cacheline for struct per_cpu_pages. THP will have 2 PCP lists, one PCP list is used by MOVABLE allocation, and the other PCP list is used by UNMOVABLE allocation. MOVABLE allocation contains GPF_MOVABLE, and UNMOVABLE allocation contains GFP_UNMOVABLE and GFP_RECLAIMABLE. Fixes: 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") Signed-off-by: yangge Acked-by: Mel Gorman --- include/linux/mmzone.h | 9 ++++----- mm/page_alloc.c | 9 +++++++-- 2 files changed, 11 insertions(+), 7 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index b7546dd..cb7f265 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -656,13 +656,12 @@ enum zone_watermarks { }; /* - * One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. One additional list - * for THP which will usually be GFP_MOVABLE. Even if it is another type, - * it should not contribute to serious fragmentation causing THP allocation - * failures. + * One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. Two additional lists + * are added for THP. One PCP list is used by GPF_MOVABLE, and the other PCP list + * is used by GFP_UNMOVABLE and GFP_RECLAIMABLE. */ #ifdef CONFIG_TRANSPARENT_HUGEPAGE -#define NR_PCP_THP 1 +#define NR_PCP_THP 2 #else #define NR_PCP_THP 0 #endif diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8f416a0..0a837e6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -504,10 +504,15 @@ static void bad_page(struct page *page, const char *reason) static inline unsigned int order_to_pindex(int migratetype, int order) { + bool __maybe_unused movable; + #ifdef CONFIG_TRANSPARENT_HUGEPAGE if (order > PAGE_ALLOC_COSTLY_ORDER) { VM_BUG_ON(order != HPAGE_PMD_ORDER); - return NR_LOWORDER_PCP_LISTS; + + movable = migratetype == MIGRATE_MOVABLE; + + return NR_LOWORDER_PCP_LISTS + movable; } #else VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER); @@ -521,7 +526,7 @@ static inline int pindex_to_order(unsigned int pindex) int order = pindex / MIGRATE_PCPTYPES; #ifdef CONFIG_TRANSPARENT_HUGEPAGE - if (pindex == NR_LOWORDER_PCP_LISTS) + if (pindex >= NR_LOWORDER_PCP_LISTS) order = HPAGE_PMD_ORDER; #else VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);