From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 94A52C44501 for ; Thu, 16 Jul 2026 10:58:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=B3DV0QU7OKveHee7CAK9wnIsCiPz/cIhJ0JoXZwda3Q=; b=jWF/eQLykttwnOB1D6M9gOrjyr ZtXxsOiucsZhE111FED3yMNwSLupCGehRUGQ6K4JhtKFbxgyKfJ8Hn9Za8iXV+k1NQBNi1CDzgoiz 73fQIJCw/Bdl4lvly26zPMsBmCcXI83tKnxSTubGxoew1qAVUcWC0GPrcAxAotvvGN4i5rr6jN69g m5+SP7wQ/8Amg4CS7dawZbYPumdlRlStkN1ksRivJYuqtKAsyei/A9s2gaU6qYibTC+YQyS4WpPwP R7JsEcYhpUgl1B0OIs+kSXs02qADyfF9jRZAEGufl2fE3VdG0LzNofESIvWv8ZeYr1UBXoRHHjFpR YrEoGg3A==; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/15/26 14:08, 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 > Reviewed-by: Dev Jain > --- > mm/vmalloc.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 80 insertions(+), 2 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index a1e025120e9df..92f9cd5e9def5 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3557,6 +3557,84 @@ static inline unsigned int vm_shift(pgprot_t prot, unsigned long size) > 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) Why pass in pages, idx when you can really just pass pages+idx? And just call it "nr_pages" instead of "max_steps". > +{ > + unsigned long pfn; > + 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); > + pfn = page_to_pfn(pages[idx]); > + > + /* Limit order by pfn alignment */ > + if (pfn > 0) > + order = min_t(int, order, __ffs(pfn)); Wouldn't it make sense to determine that before you call num_pages_contiguous? Because then, you can just scan to that maximum instead of the given nr_pages. > + > + if (vm_shift(prot, PAGE_SIZE << order) == PAGE_SHIFT) > + return 0; > + > + 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; "nr_pages" ? Also, can be const. > + 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); Is the indentation on the second parameter line off? > + 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); Having two indices, i and idx, is just confusing. The whole function is a bit overly complicated. Does it really buy us much to batch over vmap_pages_range_noflush_walk() calling with the same shift? > + > + 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. "small pages" is odd. Maybe "Once we fail to batch pages, we expect to fail batching for all remaining pages, so just give up." > + */ > + 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 > @@ -3600,8 +3678,8 @@ 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) { Nit: single line would make that nicer to read. -- Cheers, David