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X-CRM114-Status: GOOD ( 21.47 ) 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 Wed, Sep 17, 2025 at 11:48:29PM +0800, alexjlzheng@gmail.com wrote: > From: Jinliang Zheng > > After commit 6eb82f994026 ("x86/mm: Pre-allocate P4D/PUD pages for > vmalloc area"), we don't need to synchronize kernel mappings in the > vmalloc area on x86_64. Right. > And commit 58a18fe95e83 ("x86/mm/64: Do not sync vmalloc/ioremap > mappings") actually does this. Right. > But commit 6659d0279980 ("x86/mm/64: define ARCH_PAGE_TABLE_SYNC_MASK > and arch_sync_kernel_mappings()") breaks this. Good point. > This patch introduces ARCH_PAGE_TABLE_SYNC_MASK_VMALLOC to avoid > unnecessary kernel mappings synchronization of the vmalloc area. > > Fixes: 6659d0279980 ("x86/mm/64: define ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings()") The commit is getting backported to -stable kernels. Do you think this can cause a visible performance regression from user point of view, or it's just a nice optimization to have? (and any data to support?) > Signed-off-by: Jinliang Zheng > --- > arch/arm/include/asm/page.h | 3 ++- > arch/x86/include/asm/pgtable-2level_types.h | 3 ++- > arch/x86/include/asm/pgtable-3level_types.h | 3 ++- > include/linux/pgtable.h | 4 ++++ > mm/memory.c | 2 +- > mm/vmalloc.c | 6 +++--- > 6 files changed, 14 insertions(+), 7 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 0ba4f6b71847..cd2488043f8f 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3170,7 +3170,7 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr, > break; > } while (pgd++, addr = next, addr != end); > > - if (mask & ARCH_PAGE_TABLE_SYNC_MASK) > + if (mask & ARCH_PAGE_TABLE_SYNC_MASK_VMALLOC) > arch_sync_kernel_mappings(start, start + size); But vmalloc is not the only user of apply_to_page_range()? -- Cheers, Harry / Hyeonggon