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 429E0C77B72 for ; Thu, 20 Apr 2023 07:44:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233998AbjDTHoM (ORCPT ); Thu, 20 Apr 2023 03:44:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229749AbjDTHoK (ORCPT ); Thu, 20 Apr 2023 03:44:10 -0400 Received: from out30-99.freemail.mail.aliyun.com (out30-99.freemail.mail.aliyun.com [115.124.30.99]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37FE940F5 for ; Thu, 20 Apr 2023 00:44:08 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R111e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046060;MF=xhao@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0VgY3EAD_1681976643; Received: from 30.240.106.197(mailfrom:xhao@linux.alibaba.com fp:SMTPD_---0VgY3EAD_1681976643) by smtp.aliyun-inc.com; Thu, 20 Apr 2023 15:44:05 +0800 Message-ID: <97e79078-69e8-e387-9e77-a4d741eace4e@linux.alibaba.com> Date: Thu, 20 Apr 2023 15:44:03 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH] mm,unmap: avoid flushing TLB in batch if PTE is inaccessible To: Huang Ying , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel test robot , Nadav Amit , Mel Gorman , Hugh Dickins , Matthew Wilcox , David Hildenbrand References: <20230410075224.827740-1-ying.huang@intel.com> From: haoxin In-Reply-To: <20230410075224.827740-1-ying.huang@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2023/4/10 下午3:52, Huang Ying 写道: > 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/ab92aaddf1b52ede15e2c608696c36765a2602c1.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 > --- > 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, struct vm_area_struct *vma, > */ > pteval = ptep_get_and_clear(mm, address, pvmw.pte); > > - 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 = ptep_clear_flush(vma, address, pvmw.pte); > } > @@ -1963,7 +1964,8 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, > */ > pteval = ptep_get_and_clear(mm, address, pvmw.pte); > > - set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); > + if (pte_accessible(mm, pteval)) > + set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); Just a advice, can you put pte_accessible() into set_tlb_ubc_flush_pendin(), just like ptep_clear_flush(); so that we no need to add  if (pte_accessible()) in per place where call set_tlb_ubc_flush_pending(); > } else { > pteval = ptep_clear_flush(vma, address, pvmw.pte); > }