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Sat, 29 Jun 2024 19:15:40 +0800 Subject: Re: [PATCH net-next v9 10/13] mm: page_frag: introduce prepare/probe/commit API To: Alexander H Duyck , , , CC: , , Andrew Morton , References: <20240625135216.47007-1-linyunsheng@huawei.com> <20240625135216.47007-11-linyunsheng@huawei.com> <33c3c7fc00d2385e741dc6c9be0eade26c30bd12.camel@gmail.com> From: Yunsheng Lin Message-ID: <38da183b-92ba-ce9d-5472-def199854563@huawei.com> Date: Sat, 29 Jun 2024 19:15:39 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <33c3c7fc00d2385e741dc6c9be0eade26c30bd12.camel@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.69.30.204] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemf200006.china.huawei.com (7.185.36.61) X-Stat-Signature: x1rcenwfkuaaip346y1tu5q57nms9n3b X-Rspamd-Queue-Id: 9D03840013 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1719659746-119892 X-HE-Meta: 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 Jq7Z4jLK iMDSvEQPyPi2Q7j2qR7MmNcbIjbgsHztHrKiqOat4P0+5UqVKYabty+gqHQxla/B9sls55feOp1GQ/sS6p1u0vz5ZhHI201x7B4hdRHqih8k/LADjD9kthN2ctc8jU+SvBU7X+iAIFJz7XVwwruA8D4soylEwzH0zr4EGbgOLclYz68IzjblKAUB8oaFS2RFDXvOstKrVbmd9V79eydh7+JrRBlJ/WKlbl+91Hxt980BQvmU/8KpG6PVgyyWz5/mgcd0OU84TDbAgIqYZGIMxkREvc5OxmZmKl5YGss95Di2K7GgmAOGD65X8rKznTEV52qgvRfh76IKT2uM= 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: On 2024/6/29 6:35, Alexander H Duyck wrote: > On Tue, 2024-06-25 at 21:52 +0800, Yunsheng Lin wrote: >> There are many use cases that need minimum memory in order >> for forward progress, but more performant if more memory is >> available or need to probe the cache info to use any memory >> available for frag caoleasing reason. >> >> Currently skb_page_frag_refill() API is used to solve the >> above use cases, but caller needs to know about the internal >> detail and access the data field of 'struct page_frag' to >> meet the requirement of the above use cases and its >> implementation is similar to the one in mm subsystem. >> >> To unify those two page_frag implementations, introduce a >> prepare API to ensure minimum memory is satisfied and return >> how much the actual memory is available to the caller and a >> probe API to report the current available memory to caller >> without doing cache refilling. The caller needs to either call >> the commit API to report how much memory it actually uses, or >> not do so if deciding to not use any memory. >> >> As next patch is about to replace 'struct page_frag' with >> 'struct page_frag_cache' in linux/sched.h, which is included >> by the asm-offsets.s, using the virt_to_page() in the inline >> helper of page_frag_cache.h cause a "'vmemmap' undeclared" >> compiling error for asm-offsets.s, use a macro for probe API >> to avoid that compiling error. >> >> CC: Alexander Duyck >> Signed-off-by: Yunsheng Lin >> --- >> include/linux/page_frag_cache.h | 82 +++++++++++++++++++++++ >> mm/page_frag_cache.c | 114 ++++++++++++++++++++++++++++++++ >> 2 files changed, 196 insertions(+) >> >> diff --git a/include/linux/page_frag_cache.h b/include/linux/page_frag_cache.h >> index b33904d4494f..e95d44a36ec9 100644 >> --- a/include/linux/page_frag_cache.h >> +++ b/include/linux/page_frag_cache.h >> @@ -4,6 +4,7 @@ >> #define _LINUX_PAGE_FRAG_CACHE_H >> >> #include >> +#include >> >> #define PAGE_FRAG_CACHE_MAX_SIZE __ALIGN_MASK(32768, ~PAGE_MASK) >> #define PAGE_FRAG_CACHE_MAX_ORDER get_order(PAGE_FRAG_CACHE_MAX_SIZE) >> @@ -87,6 +88,9 @@ static inline unsigned int page_frag_cache_page_size(struct encoded_va *encoded_ >> >> void page_frag_cache_drain(struct page_frag_cache *nc); >> void __page_frag_cache_drain(struct page *page, unsigned int count); >> +struct page *page_frag_alloc_pg(struct page_frag_cache *nc, >> + unsigned int *offset, unsigned int fragsz, >> + gfp_t gfp); >> void *__page_frag_alloc_va_align(struct page_frag_cache *nc, >> unsigned int fragsz, gfp_t gfp_mask, >> unsigned int align_mask); >> @@ -99,12 +103,90 @@ static inline void *page_frag_alloc_va_align(struct page_frag_cache *nc, >> return __page_frag_alloc_va_align(nc, fragsz, gfp_mask, -align); >> } >> >> +static inline unsigned int page_frag_cache_page_offset(const struct page_frag_cache *nc) >> +{ >> + return page_frag_cache_page_size(nc->encoded_va) - nc->remaining; >> +} >> + >> static inline void *page_frag_alloc_va(struct page_frag_cache *nc, >> unsigned int fragsz, gfp_t gfp_mask) >> { >> return __page_frag_alloc_va_align(nc, fragsz, gfp_mask, ~0u); >> } >> >> +void *page_frag_alloc_va_prepare(struct page_frag_cache *nc, unsigned int *fragsz, >> + gfp_t gfp); >> + >> +static inline void *page_frag_alloc_va_prepare_align(struct page_frag_cache *nc, >> + unsigned int *fragsz, >> + gfp_t gfp, >> + unsigned int align) >> +{ >> + WARN_ON_ONCE(!is_power_of_2(align) || align > PAGE_SIZE); >> + nc->remaining = nc->remaining & -align; >> + return page_frag_alloc_va_prepare(nc, fragsz, gfp); >> +} >> + >> +struct page *page_frag_alloc_pg_prepare(struct page_frag_cache *nc, >> + unsigned int *offset, >> + unsigned int *fragsz, gfp_t gfp); >> + >> +struct page *page_frag_alloc_prepare(struct page_frag_cache *nc, >> + unsigned int *offset, >> + unsigned int *fragsz, >> + void **va, gfp_t gfp); >> + >> +static inline struct encoded_va *__page_frag_alloc_probe(struct page_frag_cache *nc, >> + unsigned int *offset, >> + unsigned int *fragsz, >> + void **va) >> +{ >> + struct encoded_va *encoded_va; >> + >> + *fragsz = nc->remaining; >> + encoded_va = nc->encoded_va; >> + *offset = page_frag_cache_page_size(encoded_va) - *fragsz; >> + *va = encoded_page_address(encoded_va) + *offset; >> + >> + return encoded_va; >> +} >> + >> +#define page_frag_alloc_probe(nc, offset, fragsz, va) \ >> +({ \ >> + struct page *__page = NULL; \ >> + \ >> + VM_BUG_ON(!*(fragsz)); \ >> + if (likely((nc)->remaining >= *(fragsz))) \ >> + __page = virt_to_page(__page_frag_alloc_probe(nc, \ >> + offset, \ >> + fragsz, \ >> + va)); \ >> + \ >> + __page; \ >> +}) >> + > > Why is this a macro instead of just being an inline? Are you trying to > avoid having to include a header due to the virt_to_page? Yes, you are right. I tried including different headers for virt_to_page(), and it did not work for arch/x86/kernel/asm-offsets.s, which has included linux/sched.h, and linux/sched.h need 'struct page_frag_cache' for 'struct task_struct' after this patchset, including page_frag_cache.h for sched.h causes the below compiler error: CC arch/x86/kernel/asm-offsets.s In file included from ./arch/x86/include/asm/page.h:89, from ./arch/x86/include/asm/thread_info.h:12, from ./include/linux/thread_info.h:60, from ./include/linux/spinlock.h:60, from ./include/linux/swait.h:7, from ./include/linux/completion.h:12, from ./include/linux/crypto.h:15, from arch/x86/kernel/asm-offsets.c:9: ./include/linux/page_frag_cache.h: In function ‘page_frag_alloc_align’: ./include/asm-generic/memory_model.h:37:34: error: ‘vmemmap’ undeclared (first use in this function); did you mean ‘mem_map’? 37 | #define __pfn_to_page(pfn) (vmemmap + (pfn)) | ^~~~~~~ ./include/asm-generic/memory_model.h:65:21: note: in expansion of macro ‘__pfn_to_page’ 65 | #define pfn_to_page __pfn_to_page | ^~~~~~~~~~~~~ ./arch/x86/include/asm/page.h:68:33: note: in expansion of macro ‘pfn_to_page’ 68 | #define virt_to_page(kaddr) pfn_to_page(__pa(kaddr) >> PAGE_SHIFT) | ^~~~~~~~~~~ ./include/linux/page_frag_cache.h:151:16: note: in expansion of macro ‘virt_to_page’ 151 | return virt_to_page(va); | ^~~~~~~~~~~~ ./include/asm-generic/memory_model.h:37:34: note: each undeclared identifier is reported only once for each function it appears in 37 | #define __pfn_to_page(pfn) (vmemmap + (pfn)) | ^~~~~~~ ./include/asm-generic/memory_model.h:65:21: note: in expansion of macro ‘__pfn_to_page’ 65 | #define pfn_to_page __pfn_to_page | ^~~~~~~~~~~~~ ./arch/x86/include/asm/page.h:68:33: note: in expansion of macro ‘pfn_to_page’ 68 | #define virt_to_page(kaddr) pfn_to_page(__pa(kaddr) >> PAGE_SHIFT) | ^~~~~~~~~~~ ./include/linux/page_frag_cache.h:151:16: note: in expansion of macro ‘virt_to_page’ 151 | return virt_to_page(va); Another possible way I can think of to aovid the above problem is to split the page_frag_cache.h to something like page_frag_cache/types.h and page_frag_cache/helpers.h as page_pool does, so that sched.h only need to include page_frag_cache/types.h. But I am not sure it is the correct way or it is worth the effort, what do you think about this? > > . >