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Thu, 14 May 2026 02:42:03 -0700 (PDT) From: Wen Jiang X-Google-Original-From: Wen Jiang To: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, urezki@gmail.com Cc: baohua@kernel.org, Xueyuan.chen21@gmail.com, dev.jain@arm.com, rppt@kernel.org, david@kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, ajd@linux.ibm.com, linux-kernel@vger.kernel.org, Wen Jiang , Xueyuan Chen Subject: [PATCH v2 5/7] mm/vmalloc: map contiguous pages in batches for vmap() if possible Date: Thu, 14 May 2026 17:41:06 +0800 Message-Id: <20260514094108.2016201-6-jiangwen6@xiaomi.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260514094108.2016201-1-jiangwen6@xiaomi.com> References: <20260514094108.2016201-1-jiangwen6@xiaomi.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: "Barry Song (Xiaomi)" In many cases, the pages passed to vmap() may include high-order pages. For example, the systemheap often allocates pages in descending order: order 8, then 4, then 0. Currently, vmap() iterates over every page individually—even pages inside a high-order block are handled one by one. This patch detects physically contiguous pages (regardless of whether they are compound or non-compound) by scanning with num_pages_contiguous(), and maps them as a single contiguous block whenever possible. The first page's pfn must be aligned to the mapping order for the batched mapping to be used. Pages with the same page_shift are coalesced and mapped via vmap_pages_range_noflush_walk() to avoid page table rewalk. Signed-off-by: Barry Song (Xiaomi) Co-developed-by: Dev Jain Signed-off-by: Dev Jain Signed-off-by: Wen Jiang Tested-by: Xueyuan Chen --- mm/vmalloc.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 73 insertions(+), 2 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 516d40650..c30a7673e 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3520,6 +3520,77 @@ void vunmap(const void *addr) } EXPORT_SYMBOL(vunmap); +static inline int get_vmap_batch_order(struct page **pages, + unsigned int max_steps, unsigned int idx) +{ + unsigned int nr_contig; + int order; + + if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMAP) || + ioremap_max_page_shift == PAGE_SHIFT) + return 0; + + nr_contig = num_pages_contiguous(&pages[idx], max_steps); + if (nr_contig < 2) + return 0; + + order = fls(nr_contig) - 1; + + if (arch_vmap_pte_supported_shift(PAGE_SIZE << order) == PAGE_SHIFT) + return 0; + + /* Ensure the first page's pfn is aligned to the order */ + if (!IS_ALIGNED(page_to_pfn(pages[idx]), 1 << order)) + return 0; + + return order; +} + +static int __vmap_huge(unsigned long addr, unsigned long end, + pgprot_t prot, struct page **pages) +{ + unsigned int count = (end - addr) >> PAGE_SHIFT; + unsigned int prev_shift = 0, idx = 0; + unsigned long map_addr = addr; + int err; + + err = kmsan_vmap_pages_range_noflush(addr, end, prot, pages, + PAGE_SHIFT, GFP_KERNEL); + if (err) + goto out; + + for (unsigned int i = 0; i < count; ) { + unsigned int shift = PAGE_SHIFT + + get_vmap_batch_order(pages, count - i, i); + + if (!i) + prev_shift = shift; + + if (shift != prev_shift) { + err = vmap_pages_range_noflush_walk(map_addr, addr, + prot, pages + idx, + min(prev_shift, PMD_SHIFT)); + if (err) + goto out; + prev_shift = shift; + map_addr = addr; + idx = i; + } + + addr += 1UL << shift; + i += 1U << (shift - PAGE_SHIFT); + } + + /* Remaining */ + if (map_addr < end) + err = vmap_pages_range_noflush_walk(map_addr, end, + prot, pages + idx, min(prev_shift, PMD_SHIFT)); + +out: + flush_cache_vmap(addr, end); + return err; +} + /** * vmap - map an array of pages into virtually contiguous space * @pages: array of page pointers @@ -3563,8 +3634,8 @@ void *vmap(struct page **pages, unsigned int count, return NULL; addr = (unsigned long)area->addr; - if (vmap_pages_range(addr, addr + size, pgprot_nx(prot), - pages, PAGE_SHIFT) < 0) { + if (__vmap_huge(addr, addr + size, pgprot_nx(prot), + pages) < 0) { vunmap(area->addr); return NULL; } -- 2.34.1