From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D48EB2DCC05 for ; Tue, 14 Jul 2026 04:59:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784005162; cv=none; b=Ei/7bvB1tXptXShyheopWH6uAituMlKksR0jwwP6+vpB9Y3Uyzcv+msA5s1hOVXNlajNUOuOeRIpYrMJQGV9ra+bmnqKjw3OUxyIcXdmJ1A7948wqCPj9D9UhmAyY0NkaKFOz3RD3lsm9cxH5gBLmaaTtrbgPqfNLg3f82riDCQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784005162; c=relaxed/simple; bh=hdQIJRcFrMnwMJI9ziOCW4Y68+P83FaYpP9RkJTdKVU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=nwYgnEkNDq/jwQokbD/UhcGVv12t+n/Wf9X6+G7A4uOUd9tfVE70PvzlsUBoQgqk8weVVgZ4lvshkG309bVILozy9buOQIWppG7llTxOayFrd1aRoEJdrpOckiqw9WpC/4UCupjXEIdRtFmy1WEUOr00xK87DfZynul/mXc8sNI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=C14wT9XV; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="C14wT9XV" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BB2081570; Mon, 13 Jul 2026 21:59:14 -0700 (PDT) Received: from [10.164.148.52] (unknown [10.164.148.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0853A3F7B4; Mon, 13 Jul 2026 21:59:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784005159; bh=hdQIJRcFrMnwMJI9ziOCW4Y68+P83FaYpP9RkJTdKVU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=C14wT9XVQrQyxn6c7vjT1nH48hKNL6FrbVNbRRK5Jt5xMgXuevqbO2JBAkotu4XBl nsVWl20kGja9VA+gZF24BFiEuz514qH5y4dy5r5rTz+XAlnfPQ24YsQaaAo1YBq3d6 eKy1BVnUWIYKKDQUKRHDfN4mOv80GdbSmF/hgt9Y= Message-ID: <255873b5-62d3-46da-a8b0-e1dabf1fae70@arm.com> Date: Tue, 14 Jul 2026 10:29:10 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 5/6] mm/vmalloc: map contiguous pages in batches for vmap() if possible To: Wen Jiang , akpm@linux-foundation.org, catalin.marinas@arm.com, linux-mm@kvack.org, urezki@gmail.com, will@kernel.org Cc: Xueyuan.chen21@gmail.com, ajd@linux.ibm.com, anshuman.khandual@arm.com, david@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, rppt@kernel.org, ryan.roberts@arm.com, "Barry Song (Xiaomi)" , Wen Jiang , Leo Yan References: <20260709073823.6643-1-jiangwen6@xiaomi.com> <20260709073823.6643-6-jiangwen6@xiaomi.com> Content-Language: en-US From: Dev Jain In-Reply-To: <20260709073823.6643-6-jiangwen6@xiaomi.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 09/07/26 1:08 pm, Wen Jiang wrote: > 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 mapping order is determined by taking the > minimum of the contiguous page count and the pfn alignment, allowing > graceful degradation when pfn alignment is less than the contiguous > range. > > Pages with the same page_shift are coalesced and mapped via > vmap_pages_range_noflush_walk() to avoid page table rewalk. > > As users typically allocate memory in descending orders (e.g. > 8 → 4 → 0), once an order-0 page is encountered, we stop scanning > for contiguous pages since subsequent pages are likely order-0 as well. > > 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 > Tested-by: Leo Yan > --- > mm/vmalloc.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 85 insertions(+), 2 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d2a4d649af549..db0492151ad08 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3543,6 +3543,89 @@ void vunmap(const void *addr) > } > EXPORT_SYMBOL(vunmap); > > +static inline unsigned int vm_shift(pgprot_t prot, unsigned long size) > +{ > + if (arch_vmap_pmd_supported(prot) && size >= PMD_SIZE) > + return PMD_SHIFT; > + > + return arch_vmap_pte_supported_shift(size); > +} > + > +static inline int get_vmap_batch_order(struct page **pages, > + pgprot_t prot, unsigned int max_steps, unsigned int idx) > +{ > + unsigned int nr_contig; > + int order; > + > + if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMAP)) > + return 0; > + > + nr_contig = num_pages_contiguous(&pages[idx], max_steps); > + if (nr_contig < 2) > + return 0; > + > + order = ilog2(nr_contig); > + > + /* Limit order by pfn alignment */ > + order = min_t(int, order, __ffs(page_to_pfn(pages[idx]))); As said previously, you need to account for the case where pfn is zero. > + > + if (vm_shift(prot, PAGE_SIZE << order) == PAGE_SHIFT) > + return 0; Correct. There is no point in clamping the order by vm_shift(), because then we won't be able to batch multiple cont blocks. So in case (PAGE_SIZE << order) is a quantity less than CONT_PTE_SHIFT, simply bail out from batching. > + > + return order; > +} > + > +static int vmap_pages_range_batched(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, batch_end = addr; > + int err; > + > + err = kmsan_vmap_pages_range_noflush(addr, end, prot, pages, > + PAGE_SHIFT, GFP_KERNEL); Nit: Indentation. PAGE_SHIFT should start right below addr. Apart from these two points, nothing jumped at me. So after these are taken care of: Reviewed-by: Dev Jain > + if (err) > + goto out; > + > + for (unsigned int i = 0; i < count; ) { > + unsigned int shift = PAGE_SHIFT + > + get_vmap_batch_order(pages, prot, count - i, i); > + > + if (!i) > + prev_shift = shift; > + > + if (shift != prev_shift) { > + err = vmap_pages_range_noflush_walk(map_addr, batch_end, > + prot, pages + idx, prev_shift); > + if (err) > + goto out; > + prev_shift = shift; > + map_addr = batch_end; > + idx = i; > + } > + > + /* > + * Once small pages are encountered, the remaining pages > + * are likely small as well. > + */ > + if (shift == PAGE_SHIFT) > + break; > + > + batch_end += 1UL << shift; > + i += 1U << (shift - PAGE_SHIFT); > + } > + > + /* Remaining */ > + if (map_addr < end) > + err = vmap_pages_range_noflush_walk(map_addr, end, > + prot, pages + idx, prev_shift); > + > +out: > + flush_cache_vmap(addr, end); > + return err; > +} > + > /** > * vmap - map an array of pages into virtually contiguous space > * @pages: array of page pointers > @@ -3586,8 +3669,8 @@ 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_pages_range_batched(addr, addr + size, pgprot_nx(prot), > + pages) < 0) { > vunmap(area->addr); > return NULL; > }