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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 501FEECAAA1 for ; Fri, 9 Sep 2022 07:45:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231715AbiIIHpb (ORCPT ); Fri, 9 Sep 2022 03:45:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43470 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231652AbiIIHpM (ORCPT ); Fri, 9 Sep 2022 03:45:12 -0400 Received: from out199-15.us.a.mail.aliyun.com (out199-15.us.a.mail.aliyun.com [47.90.199.15]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66A5F132068 for ; Fri, 9 Sep 2022 00:41:46 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R551e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046056;MF=xhao@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0VP8T26d_1662709098; Received: from localhost.localdomain(mailfrom:xhao@linux.alibaba.com fp:SMTPD_---0VP8T26d_1662709098) by smtp.aliyun-inc.com; Fri, 09 Sep 2022 15:38:19 +0800 From: Xin Hao To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH V1] mm: remove update_mmu_cache() when page is zero page Date: Fri, 9 Sep 2022 15:38:15 +0800 Message-Id: <20220909073815.90046-1-xhao@linux.alibaba.com> X-Mailer: git-send-email 2.31.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The zero page is never written to, so it will never has any dirty cache lines, and therefore there no need to be flushed. Signed-off-by: Xin Hao --- mm/huge_memory.c | 1 - mm/memory.c | 5 ++++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 8a7c1b344abe..679eb425e54f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -821,7 +821,6 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf) } else { set_huge_zero_page(pgtable, vma->vm_mm, vma, haddr, vmf->pmd, zero_page); - update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); spin_unlock(vmf->ptl); } } else { diff --git a/mm/memory.c b/mm/memory.c index 4ba73f5aa8bb..3650e7cae26f 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4034,6 +4034,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) struct page *page; vm_fault_t ret = 0; pte_t entry; + bool is_zero_page = false; /* File mapping without ->vm_ops ? */ if (vma->vm_flags & VM_SHARED) @@ -4075,6 +4076,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) pte_unmap_unlock(vmf->pte, vmf->ptl); return handle_userfault(vmf, VM_UFFD_MISSING); } + is_zero_page = true; goto setpte; } @@ -4126,7 +4128,8 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry); /* No need to invalidate - it was non-present before */ - update_mmu_cache(vma, vmf->address, vmf->pte); + if (!is_zero_page) + update_mmu_cache(vma, vmf->address, vmf->pte); unlock: pte_unmap_unlock(vmf->pte, vmf->ptl); return ret; -- 2.31.0