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([2409:8a55:301b:e120:88bd:a0fb:c6d6:c4a2]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2e06e16d6d2sm13168168a91.2.2024.10.01.00.59.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Oct 2024 00:59:43 -0700 (PDT) From: Yunsheng Lin X-Google-Original-From: Yunsheng Lin To: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Yunsheng Lin , Alexander Duyck , Andrew Morton , linux-mm@kvack.org Subject: [PATCH net-next v19 06/14] mm: page_frag: reuse existing space for 'size' and 'pfmemalloc' Date: Tue, 1 Oct 2024 15:58:49 +0800 Message-Id: <20241001075858.48936-7-linyunsheng@huawei.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241001075858.48936-1-linyunsheng@huawei.com> References: <20241001075858.48936-1-linyunsheng@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 Signed-off-by: Yunsheng Lin --- include/linux/mm_types_task.h | 19 +++++---- include/linux/page_frag_cache.h | 26 +++++++++++- mm/page_frag_cache.c | 75 +++++++++++++++++++++++---------- 3 files changed, 88 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 <=3D 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; }; =20 /* Track pages that require TLB flushes */ diff --git a/include/linux/page_frag_cache.h b/include/linux/page_frag_cach= e.h index 0a52f7a179c8..75aaad6eaea2 100644 --- a/include/linux/page_frag_cache.h +++ b/include/linux/page_frag_cache.h @@ -3,18 +3,40 @@ #ifndef _LINUX_PAGE_FRAG_CACHE_H #define _LINUX_PAGE_FRAG_CACHE_H =20 +#include #include #include #include =20 +#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) +#define PAGE_FRAG_CACHE_PFMEMALLOC_SHIFT 8 +#define PAGE_FRAG_CACHE_PFMEMALLOC_BIT BIT(PAGE_FRAG_CACHE_PFMEMALLOC_SHI= FT) +#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 +#define PAGE_FRAG_CACHE_PFMEMALLOC_SHIFT 0 +#define PAGE_FRAG_CACHE_PFMEMALLOC_BIT BIT(PAGE_FRAG_CACHE_PFMEMALLOC_SHI= FT) +#endif + +static inline bool page_frag_encoded_page_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 =3D NULL; + nc->encoded_page =3D 0; } =20 static inline bool page_frag_cache_is_pfmemalloc(struct page_frag_cache *n= c) { - return !!nc->pfmemalloc; + return page_frag_encoded_page_pfmemalloc(nc->encoded_page); } =20 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..cf9375a81a64 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. */ =20 +#include #include #include #include @@ -19,9 +20,41 @@ #include #include "internal.h" =20 +static unsigned long page_frag_encode_page(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 >=3D PAGE_SIZE); + + return (unsigned long)page_address(page) | + (order & PAGE_FRAG_CACHE_ORDER_MASK) | + ((unsigned long)pfmemalloc << PAGE_FRAG_CACHE_PFMEMALLOC_SHIFT); +} + +static unsigned long page_frag_encoded_page_order(unsigned long encoded_pa= ge) +{ + return encoded_page & PAGE_FRAG_CACHE_ORDER_MASK; +} + +static void *page_frag_encoded_page_address(unsigned long encoded_page) +{ + return (void *)(encoded_page & PAGE_MASK); +} + +static struct page *page_frag_encoded_page_ptr(unsigned long encoded_page) +{ + return virt_to_page((void *)encoded_page); +} + +static unsigned int page_frag_cache_page_size(unsigned long encoded_page) +{ + return PAGE_SIZE << page_frag_encoded_page_order(encoded_page); +} + static struct page *__page_frag_cache_refill(struct page_frag_cache *nc, gfp_t gfp_mask) { + unsigned long order =3D PAGE_FRAG_CACHE_MAX_ORDER; struct page *page =3D NULL; gfp_t gfp =3D gfp_mask; =20 @@ -30,23 +63,26 @@ static struct page *__page_frag_cache_refill(struct pag= e_frag_cache *nc, __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC; page =3D alloc_pages_node(NUMA_NO_NODE, gfp_mask, PAGE_FRAG_CACHE_MAX_ORDER); - nc->size =3D page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE; #endif - if (unlikely(!page)) + if (unlikely(!page)) { page =3D alloc_pages_node(NUMA_NO_NODE, gfp, 0); + order =3D 0; + } =20 - nc->va =3D page ? page_address(page) : NULL; + nc->encoded_page =3D page ? + page_frag_encode_page(page, order, page_is_pfmemalloc(page)) : 0; =20 return page; } =20 void page_frag_cache_drain(struct page_frag_cache *nc) { - if (!nc->va) + if (!nc->encoded_page) return; =20 - __page_frag_cache_drain(virt_to_head_page(nc->va), nc->pagecnt_bias); - nc->va =3D NULL; + __page_frag_cache_drain(page_frag_encoded_page_ptr(nc->encoded_page), + nc->pagecnt_bias); + nc->encoded_page =3D 0; } EXPORT_SYMBOL(page_frag_cache_drain); =20 @@ -63,35 +99,29 @@ void *__page_frag_alloc_align(struct page_frag_cache *n= c, unsigned int fragsz, gfp_t gfp_mask, unsigned int align_mask) { -#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) - unsigned int size =3D nc->size; -#else - unsigned int size =3D PAGE_SIZE; -#endif - unsigned int offset; + unsigned long encoded_page =3D nc->encoded_page; + unsigned int size, offset; struct page *page; =20 - if (unlikely(!nc->va)) { + if (unlikely(!encoded_page)) { refill: page =3D __page_frag_cache_refill(nc, gfp_mask); if (!page) return NULL; =20 -#if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) - /* if size can vary use size else just use PAGE_SIZE */ - size =3D nc->size; -#endif + encoded_page =3D 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); =20 /* reset page count bias and offset to start of new frag */ - nc->pfmemalloc =3D page_is_pfmemalloc(page); nc->pagecnt_bias =3D PAGE_FRAG_CACHE_MAX_SIZE + 1; nc->offset =3D 0; } =20 + size =3D page_frag_cache_page_size(encoded_page); offset =3D __ALIGN_KERNEL_MASK(nc->offset, ~align_mask); if (unlikely(offset + fragsz > size)) { if (unlikely(fragsz > PAGE_SIZE)) { @@ -107,13 +137,14 @@ void *__page_frag_alloc_align(struct page_frag_cache = *nc, return NULL; } =20 - page =3D virt_to_page(nc->va); + page =3D page_frag_encoded_page_ptr(encoded_page); =20 if (!page_ref_sub_and_test(page, nc->pagecnt_bias)) goto refill; =20 - if (unlikely(nc->pfmemalloc)) { - free_unref_page(page, compound_order(page)); + if (unlikely(page_frag_encoded_page_pfmemalloc(encoded_page))) { + free_unref_page(page, + page_frag_encoded_page_order(encoded_page)); goto refill; } =20 @@ -128,7 +159,7 @@ void *__page_frag_alloc_align(struct page_frag_cache *n= c, nc->pagecnt_bias--; nc->offset =3D offset + fragsz; =20 - return nc->va + offset; + return page_frag_encoded_page_address(encoded_page) + offset; } EXPORT_SYMBOL(__page_frag_alloc_align); =20 --=20 2.34.1