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 3B7F23750AC for ; Mon, 13 Jul 2026 15:19:40 +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=1783955983; cv=none; b=qZMfoSnI5pjrqadyzVzIRXL2j6hhAGGBTA3HX/3LBgs9mT/dOK3nRu/DQCjxYhVvOe58s84+qBJzyn2gnF9IxnhiKQX2HZ47nx3NRC8Iv5KE4Q3+SHGTgfhB2jXih0TNwkGdpo0BLdf3mX6LHoE/UdQKrmCfjCRoT+Vj9ew79Sc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783955983; c=relaxed/simple; bh=6itNocGqdstfsGVwFY8Fldnsbq94BxJ1jweYynvGIyM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Iek3VQf9mME8M20ufFDqPGjxHy7ZGTud2yHUvRZP6mpMlU27emYYC1e9x10gjHWKVThm8LTMFHhrYvHLZ8FxTUG1EVwvTNTrmLDAC8yr6fAc50ERAXlJLJ7t/SR5EgFsodJWN6yPmPlu/YSxMKDCjnVTWTTJfEa1GRglKcXeW5s= 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=eNOeX5wB; 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="eNOeX5wB" 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 2E8461576; Mon, 13 Jul 2026 08:19:36 -0700 (PDT) Received: from [10.164.19.52] (unknown [10.164.19.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0F5B23F93E; Mon, 13 Jul 2026 08:19:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783955980; bh=6itNocGqdstfsGVwFY8Fldnsbq94BxJ1jweYynvGIyM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=eNOeX5wBC+l/3/3tHLXTnRTariYyyEtBlRXR+rHI/BOZuLuOp6vUDOhXvIHFDkrhg 4mvmbYS8yYUrx8p84rbdDf/KcvkLxe5gops5cM9kGRNw7IWd8jHuVrQslZk+3VOU0D tTRvCWvoP3paIHCoH71B9srt9i0aGKkHhZKhaS5E= Message-ID: Date: Mon, 13 Jul 2026 20:49:33 +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); > +} Need to throw in a preparatory patch for this, which will (in addition to introduction of the vm_shift() function) do: diff --git a/mm/vmalloc.c b/mm/vmalloc.c index afaa14ebf17bb..dac87e1cd484b 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4175,10 +4175,7 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, * supporting them. */ - if (arch_vmap_pmd_supported(prot) && size >= PMD_SIZE) - shift = PMD_SHIFT; - else - shift = arch_vmap_pte_supported_shift(size); + shift = vm_shift(prot, size); align = max(original_align, 1UL << shift); } > + > +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]))); You missed Sashiko's point here :) the pfn may be zero and this will blow up. You can just first derive the pfn and do the clamping only when pfn > 0. > + > + if (vm_shift(prot, PAGE_SIZE << order) == PAGE_SHIFT) > + return 0; > + > + return order; > +} > +