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 345BB2DEA98 for ; Tue, 14 Jul 2026 05:33:42 +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=1784007225; cv=none; b=WZDjoLLwuqQXAdm5U3Jr9Ka85ldtxYIefl9lQgjoETVElmXLFAHsM1e6tkbt1vZMXxx48qcOK4rGc6P1lvBmBQVMKs7mcQZRxauSR1beOt696Al/4U2eXffCJFT2/SDua+O0ua9FeYts82/EnKhNCr0Q2eOSHk+1MkZveFsmHZY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784007225; c=relaxed/simple; bh=hccglgIXGsjwDzVnD98+WSP/z7D0qxzcLTBTl50S9mg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Pte1u8kQk/xSCA81ceOoH4mLo5l1im8nSW/i81AItd+ngjixIyL+ddMnirrc2TRIW6KVVPlNPHl+eTLzqGVCwyLDueduVqyjRTjZe2HbvHhIZP9NVUFrQW1CUY09OUPqKdWX2sZtX8Qubm0t/K9FB5hy1Z/M+jksaw22nXPWkMQ= 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=FSOAa8YN; 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="FSOAa8YN" 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 2A4AC339; Mon, 13 Jul 2026 22:33:38 -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 6FDB83F7D8; Mon, 13 Jul 2026 22:33:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784007222; bh=hccglgIXGsjwDzVnD98+WSP/z7D0qxzcLTBTl50S9mg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=FSOAa8YNN3CVVYMjJlByEEDvCp3N6RiO2oahs9L5zy3NLSdL4eotRZOOzLXBgsR6c QeIYYS2MnJjijJddDjToSP50t6vArkTP40fqUyhWbBaoCbjr/zmfwyDXdqfoJjJoEn U6REtT/KH2W5L1HtBWEbunXMgohTA6E6QD/jFSyw= Message-ID: Date: Tue, 14 Jul 2026 11:03:34 +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 Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, linux-mm@kvack.org, urezki@gmail.com, will@kernel.org, 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 14/07/26 10:46 am, Wen Jiang wrote: > On Mon, 13 Jul 2026 at 23:19, Dev Jain wrote: >> >> >> >> 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: >> > > Hi Dev, > > Your suggestion is to extract "vm_shift" into a separate patch, say > Patch 5, to make it a common utility function just like Patch 3. And > move the existing code that can use vm_shift into this new patch as > well, correct? Yes it will look like the current patch 3. So before the current patch 5, you can have a patch introducing vm_shift and making the code chunk in __vmalloc_node_range_noprof() call it. > > Thanks, > Wen > >> 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. >> >> > > Will fix this. > > Thanks, > Wen >> >>> + >>> + if (vm_shift(prot, PAGE_SIZE << order) == PAGE_SHIFT) >>> + return 0; >>> + >>> + return order; >>> +} >>> +