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Mon, 28 Oct 2024 20:00:17 +0800 (CST) Received: from localhost.localdomain (10.90.30.45) by dggpemf200006.china.huawei.com (7.185.36.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 28 Oct 2024 20:00:16 +0800 From: Yunsheng Lin To: , , CC: , , Yunsheng Lin , Alexander Duyck , Andrew Morton , Linux-MM , Alexander Duyck Subject: [PATCH net-next v23 6/7] mm: page_frag: reuse existing space for 'size' and 'pfmemalloc' Date: Mon, 28 Oct 2024 19:53:41 +0800 Message-ID: <20241028115343.3405838-7-linyunsheng@huawei.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20241028115343.3405838-1-linyunsheng@huawei.com> References: <20241028115343.3405838-1-linyunsheng@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.90.30.45] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemf200006.china.huawei.com (7.185.36.61) X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 752638000E X-Stat-Signature: ukfcfw5wsi69zp8n9x5djowisatzax89 X-Rspam-User: X-HE-Tag: 1730116778-923955 X-HE-Meta: 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 ch4yS+fr +tCprGXp1kNognaZ3+bYrxiT/Xg3pt/gm3rg3kryJpwGwx2mXmOrF2aq1ddWE7RgXf+VFfrs+BWyDiKhfqnOO732i5wjXwAgv4hZD+4oP4eEM4qyDXYcfw1JxIe6RkKQh0iznLYyU4R9Z93NTU6lCMDZZmaNf76X3ukNWbXrUwKudfOq+1RIFblDFDbT7K7nZX9gTfFO1ZWx5DO0/swUmEQMrYOQksQUI1gvCDIgaDau0UcuFrAgRBVARIRHtly8d2RKoTtKc/35Ezl3+pXvBsOefklovw1Lw5h2Rec5ULSVPkEHi5zCHoBMAd1tnMUTliDwd2lYEiiwohPFBPpa7hg0qFZWagi+Jf8+BmmSi/uAN2EMu2pRw4JEhPe3RIW/4q2zFar1QnKh/MrY2IPq7INTtcHATgKVEL3cxYlGj7EvSYmk= 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: Currently there is one 'struct page_frag' for every 'struct sock' and 'struct task_struct', we are about to replace the 'struct page_frag' with 'struct page_frag_cache' for them. Before begin the replacing, we need to ensure the size of 'struct page_frag_cache' is not bigger than the size of 'struct page_frag', as there may be tens of thousands of 'struct sock' and 'struct task_struct' instances in the system. By or'ing the page order & pfmemalloc with lower bits of 'va' instead of using 'u16' or 'u32' for page size and 'u8' for pfmemalloc, we are able to avoid 3 or 5 bytes space waste. And page address & pfmemalloc & order is unchanged for the same page in the same 'page_frag_cache' instance, it makes sense to fit them together. After this patch, the size of 'struct page_frag_cache' should be the same as the size of 'struct page_frag'. CC: Alexander Duyck CC: Andrew Morton CC: Linux-MM Signed-off-by: Yunsheng Lin Reviewed-by: Alexander Duyck --- include/linux/mm_types_task.h | 19 +++++---- include/linux/page_frag_cache.h | 24 ++++++++++- mm/page_frag_cache.c | 70 ++++++++++++++++++++++----------- 3 files changed, 81 insertions(+), 32 deletions(-) diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h index 0ac6daebdd5c..a82aa80c0ba4 100644 --- a/include/linux/mm_types_task.h +++ b/include/linux/mm_types_task.h @@ -47,18 +47,21 @@ struct page_frag { #define PAGE_FRAG_CACHE_MAX_SIZE __ALIGN_MASK(32768, ~PAGE_MASK) #define PAGE_FRAG_CACHE_MAX_ORDER get_order(PAGE_FRAG_CACHE_MAX_SIZE) struct page_frag_cache { - void *va; -#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) + /* encoded_page consists of the virtual address, pfmemalloc bit and + * order of a page. + */ + unsigned long encoded_page; + + /* we maintain a pagecount bias, so that we dont dirty cache line + * containing page->_refcount every time we allocate a fragment. + */ +#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) && (BITS_PER_LONG <= 32) __u16 offset; - __u16 size; + __u16 pagecnt_bias; #else __u32 offset; + __u32 pagecnt_bias; #endif - /* we maintain a pagecount bias, so that we dont dirty cache line - * containing page->_refcount every time we allocate a fragment. - */ - unsigned int pagecnt_bias; - bool pfmemalloc; }; /* Track pages that require TLB flushes */ diff --git a/include/linux/page_frag_cache.h b/include/linux/page_frag_cache.h index 0a52f7a179c8..41a91df82631 100644 --- a/include/linux/page_frag_cache.h +++ b/include/linux/page_frag_cache.h @@ -3,18 +3,38 @@ #ifndef _LINUX_PAGE_FRAG_CACHE_H #define _LINUX_PAGE_FRAG_CACHE_H +#include #include #include #include +#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) +/* Use a full byte here to enable assembler optimization as the shift + * operation is usually expecting a byte. + */ +#define PAGE_FRAG_CACHE_ORDER_MASK GENMASK(7, 0) +#else +/* Compiler should be able to figure out we don't read things as any value + * ANDed with 0 is 0. + */ +#define PAGE_FRAG_CACHE_ORDER_MASK 0 +#endif + +#define PAGE_FRAG_CACHE_PFMEMALLOC_BIT (PAGE_FRAG_CACHE_ORDER_MASK + 1) + +static inline bool encoded_page_decode_pfmemalloc(unsigned long encoded_page) +{ + return !!(encoded_page & PAGE_FRAG_CACHE_PFMEMALLOC_BIT); +} + static inline void page_frag_cache_init(struct page_frag_cache *nc) { - nc->va = NULL; + nc->encoded_page = 0; } static inline bool page_frag_cache_is_pfmemalloc(struct page_frag_cache *nc) { - return !!nc->pfmemalloc; + return encoded_page_decode_pfmemalloc(nc->encoded_page); } void page_frag_cache_drain(struct page_frag_cache *nc); diff --git a/mm/page_frag_cache.c b/mm/page_frag_cache.c index 4c8e04379cb3..a36fd09bf275 100644 --- a/mm/page_frag_cache.c +++ b/mm/page_frag_cache.c @@ -12,6 +12,7 @@ * be used in the "frags" portion of skb_shared_info. */ +#include #include #include #include @@ -19,9 +20,36 @@ #include #include "internal.h" +static unsigned long encoded_page_create(struct page *page, unsigned int order, + bool pfmemalloc) +{ + BUILD_BUG_ON(PAGE_FRAG_CACHE_MAX_ORDER > PAGE_FRAG_CACHE_ORDER_MASK); + BUILD_BUG_ON(PAGE_FRAG_CACHE_PFMEMALLOC_BIT >= PAGE_SIZE); + + return (unsigned long)page_address(page) | + (order & PAGE_FRAG_CACHE_ORDER_MASK) | + ((unsigned long)pfmemalloc * PAGE_FRAG_CACHE_PFMEMALLOC_BIT); +} + +static unsigned long encoded_page_decode_order(unsigned long encoded_page) +{ + return encoded_page & PAGE_FRAG_CACHE_ORDER_MASK; +} + +static void *encoded_page_decode_virt(unsigned long encoded_page) +{ + return (void *)(encoded_page & PAGE_MASK); +} + +static struct page *encoded_page_decode_page(unsigned long encoded_page) +{ + return virt_to_page((void *)encoded_page); +} + static struct page *__page_frag_cache_refill(struct page_frag_cache *nc, gfp_t gfp_mask) { + unsigned long order = PAGE_FRAG_CACHE_MAX_ORDER; struct page *page = NULL; gfp_t gfp = gfp_mask; @@ -30,23 +58,26 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc, __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC; page = alloc_pages_node(NUMA_NO_NODE, gfp_mask, PAGE_FRAG_CACHE_MAX_ORDER); - nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE; #endif - if (unlikely(!page)) + if (unlikely(!page)) { page = alloc_pages_node(NUMA_NO_NODE, gfp, 0); + order = 0; + } - nc->va = page ? page_address(page) : NULL; + nc->encoded_page = page ? + encoded_page_create(page, order, page_is_pfmemalloc(page)) : 0; return page; } void page_frag_cache_drain(struct page_frag_cache *nc) { - if (!nc->va) + if (!nc->encoded_page) return; - __page_frag_cache_drain(virt_to_head_page(nc->va), nc->pagecnt_bias); - nc->va = NULL; + __page_frag_cache_drain(encoded_page_decode_page(nc->encoded_page), + nc->pagecnt_bias); + nc->encoded_page = 0; } EXPORT_SYMBOL(page_frag_cache_drain); @@ -63,35 +94,29 @@ void *__page_frag_alloc_align(struct page_frag_cache *nc, unsigned int fragsz, gfp_t gfp_mask, unsigned int align_mask) { -#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) - unsigned int size = nc->size; -#else - unsigned int size = PAGE_SIZE; -#endif - unsigned int offset; + unsigned long encoded_page = nc->encoded_page; + unsigned int size, offset; struct page *page; - if (unlikely(!nc->va)) { + if (unlikely(!encoded_page)) { refill: page = __page_frag_cache_refill(nc, gfp_mask); if (!page) return NULL; -#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) - /* if size can vary use size else just use PAGE_SIZE */ - size = nc->size; -#endif + encoded_page = nc->encoded_page; + /* Even if we own the page, we do not use atomic_set(). * This would break get_page_unless_zero() users. */ page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE); /* reset page count bias and offset to start of new frag */ - nc->pfmemalloc = page_is_pfmemalloc(page); nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1; nc->offset = 0; } + size = PAGE_SIZE << encoded_page_decode_order(encoded_page); offset = __ALIGN_KERNEL_MASK(nc->offset, ~align_mask); if (unlikely(offset + fragsz > size)) { if (unlikely(fragsz > PAGE_SIZE)) { @@ -107,13 +132,14 @@ void *__page_frag_alloc_align(struct page_frag_cache *nc, return NULL; } - page = virt_to_page(nc->va); + page = encoded_page_decode_page(encoded_page); if (!page_ref_sub_and_test(page, nc->pagecnt_bias)) goto refill; - if (unlikely(nc->pfmemalloc)) { - free_unref_page(page, compound_order(page)); + if (unlikely(encoded_page_decode_pfmemalloc(encoded_page))) { + free_unref_page(page, + encoded_page_decode_order(encoded_page)); goto refill; } @@ -128,7 +154,7 @@ void *__page_frag_alloc_align(struct page_frag_cache *nc, nc->pagecnt_bias--; nc->offset = offset + fragsz; - return nc->va + offset; + return encoded_page_decode_virt(encoded_page) + offset; } EXPORT_SYMBOL(__page_frag_alloc_align);