From nobody Wed Feb 11 16:48:36 2026 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 54156C77B61 for ; Mon, 10 Apr 2023 07:52:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229831AbjDJHwr (ORCPT ); Mon, 10 Apr 2023 03:52:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229571AbjDJHwo (ORCPT ); Mon, 10 Apr 2023 03:52:44 -0400 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 810383C0A for ; Mon, 10 Apr 2023 00:52:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1681113163; x=1712649163; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=Yr48j2bIPY5fAJkFuSojw587VB/8YMUbbc+kU0mekfQ=; b=ehW1Ke8YNasHU8DAH6yqxqgeZDpVMckFOJ/T4wB2X4WMH+YWEwdhc04S kErYOnoXHIqSe7fFmR5FTMKG14JNsYnMLJ47yn/2eUsqrD7PGXvjAs7g4 eWn40cFEGmkzLqYsC+0Ah067Kyqvpw6UaO+K2ZErYZQKGpdShDyCvkph3 xH0VzuW8vnu0+aDhkmiLUYSrTM+2fSvifrvR9XgCjG1Kbwmt5TPATvo8j nGAGrgmhEQFUZY2PXXStereMSkIle2YKFG/2oHA8+UxGMMGKFdXR385lO bDzBUY5bemDCzGgQmCl/QHL00V/NuEntF/fUgnmgxVTAN9ZAJXfcLkMeX A==; X-IronPort-AV: E=McAfee;i="6600,9927,10675"; a="345969183" X-IronPort-AV: E=Sophos;i="5.98,333,1673942400"; d="scan'208";a="345969183" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Apr 2023 00:52:43 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10675"; a="681667638" X-IronPort-AV: E=Sophos;i="5.98,333,1673942400"; d="scan'208";a="681667638" Received: from yhuang6-mobl2.sh.intel.com ([10.238.7.50]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Apr 2023 00:52:40 -0700 From: Huang Ying To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , kernel test robot , Nadav Amit , Mel Gorman , Hugh Dickins , Matthew Wilcox , David Hildenbrand Subject: [PATCH] mm,unmap: avoid flushing TLB in batch if PTE is inaccessible Date: Mon, 10 Apr 2023 15:52:24 +0800 Message-Id: <20230410075224.827740-1-ying.huang@intel.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 0Day/LKP reported a performance regression for commit 7e12beb8ca2a ("migrate_pages: batch flushing TLB"). In the commit, the TLB flushing during page migration is batched. So, in try_to_migrate_one(), ptep_clear_flush() is replaced with set_tlb_ubc_flush_pending(). In further investigation, it is found that the TLB flushing can be avoided in ptep_clear_flush() if the PTE is inaccessible. In fact, we can optimize in similar way for the batched TLB flushing too to improve the performance. So in this patch, we check pte_accessible() before set_tlb_ubc_flush_pending() in try_to_unmap/migrate_one(). Tests show that the benchmark score of the anon-cow-rand-mt test case of vm-scalability test suite can improve up to 2.1% with the patch on a Intel server machine. The TLB flushing IPI can reduce up to 44.3%. Link: https://lore.kernel.org/oe-lkp/202303192325.ecbaf968-yujie.liu@intel.= com Link: https://lore.kernel.org/oe-lkp/ab92aaddf1b52ede15e2c608696c36765a2602= c1.camel@intel.com/ Fixes: 7e12beb8ca2a ("migrate_pages: batch flushing TLB") Reported-by: kernel test robot Signed-off-by: "Huang, Ying" Cc: Nadav Amit Cc: Mel Gorman Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Cc: David Hildenbrand Reviewed-by: Nadav Amit --- mm/rmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 8632e02661ac..3c7c43642d7c 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1582,7 +1582,8 @@ static bool try_to_unmap_one(struct folio *folio, str= uct vm_area_struct *vma, */ pteval =3D ptep_get_and_clear(mm, address, pvmw.pte); =20 - set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); + if (pte_accessible(mm, pteval)) + set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); } else { pteval =3D ptep_clear_flush(vma, address, pvmw.pte); } @@ -1963,7 +1964,8 @@ static bool try_to_migrate_one(struct folio *folio, s= truct vm_area_struct *vma, */ pteval =3D ptep_get_and_clear(mm, address, pvmw.pte); =20 - set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); + if (pte_accessible(mm, pteval)) + set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); } else { pteval =3D ptep_clear_flush(vma, address, pvmw.pte); } --=20 2.39.2