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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 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 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 542821C0002 X-Stat-Signature: zarn8wwnzqaji37t914x4nee7ojqu6pk X-HE-Tag: 1784007223-97343 X-HE-Meta: U2FsdGVkX1+yJduriLGk6tWDIGw+otbsZSdmmrELbRwyaUe4KGube3aF4zTppTjPxHiWxkWZklFEItjSoVuZRtNClz/7WFRVx9TRDsTtWLT94MXkyGny+7h15ggg1PIM0yBCs00dR/Hw+n3Jmgi0WYF3dzUggMzoHSfSI6onRh0a/i/ZSXPbfrpSFplq2ySd6Jx6Ox4PAeE8haRpAreys2F7iMfrJrSa8HsTMxOURCsNBIaQ1Zcv9W8xodojRL9ycONl3rm+G+Xjn03a3v1QIeRobBPfRet95wZm0BpwouYw9xNif92LRM4ncUWeLgD4EJnRrsnRXVglohjWhbyCb4lFMjBhn/KTxS3ei1hHUhNs37tHUTjE6luO/y49uqPQooDeAH3h8pnMzu2o/Did6zkTMghADHGKkN5hrZqEXm+xa3G/28wHNiIm3cIYl4R5H3zSSfGqo0A2nN55YNKDUfRKdbRHMjIWkgZsOBLqU862nuzXx9qgNNO5A9J4xMboy1tBp2FsuAB14yeYIyzSCWIkBzwYw5aHayAS6Taf4T3R1qjQJUGjlu03W5jGtxhmf1lL/ksFpWfP76D2cs8kWgftlsOMouyv2ySOXEtUIbnS96PV47vuRfOxPJtU+4mgMseDpauWqjWmKr8NCZ6QEJtAgTd4s0Kfxj8DpOvOhnD8dTZg1Gr8icc3X4cYN6/3mnRBu0Xm9S3DJISMhqflAhqzb2pA+gBO/uBFoqFGHoLM2aBuDVnWd6mthWF9HMwhcdaeDKSmNe1cV9wVHWJ0z+LE/W82+TfuwG9D1bwGfZ+hGWYTS1e0siN1ervMT5BKHkcquD+WRrS/09f5i9HjD8aoZw00Wx0NULNGdIs3tAUI78MPHedvoQLIJm8YL+H4dd29QpDg3ro4fuSsFLFakrvDP1awLzzyN7gq5F2JdXXsDq0TbMLqgP2yqp6u9CBaJq3MFE48sc/cmGviI5F EZDw5rkB F98TxKGuxxUqwzJaz+xuRbfYyRVARAu3uhPyeYDFjaum71zNtMHYsToijZ7C7lMna7T+NOoCbYfyo2qso8PIKO1V86/+eci/q3Z+V92pOxbPY5OAi+jcEZTG2g072rYJceGcH1hhwpMIjbbB9e96lrWyu32mkEBqTIRbzR8Xiaxhxwf4ahUIemgZ3aT4k3FcQHWRItMz/4jRmfVMOE4r43N+8vWY2FG5PsWPAmAPpkOp0P/XQKevSdtdokUy3gX0oDdMdhpjX2H4ZvZsPp3S/9Z9XaQhCcfkzGvTkqgoWPuTqlorBXh9EI70iG0ZonC6UW9+f13zICG0bte6xsumL7XiAw+iEmKfwppiCdT17eiZHMJY5dpaQPF1DdYmt+TMjgqZFMs+MIckqR0Taaat1iGiwKMmwaPLEdtE6qiEidCD589mpcY/Ip9I/wnpukby36UqMNdJUIRjBqbM0t73vXNbBog== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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; >>> +} >>> +