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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91AF4C2D0F4 for ; Wed, 8 Apr 2020 18:43:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6E45B2072F for ; Wed, 8 Apr 2020 18:43:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729272AbgDHSnE (ORCPT ); Wed, 8 Apr 2020 14:43:04 -0400 Received: from out30-133.freemail.mail.aliyun.com ([115.124.30.133]:41845 "EHLO out30-133.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726860AbgDHSnE (ORCPT ); Wed, 8 Apr 2020 14:43:04 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04357;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0Tv.3hCG_1586371377; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0Tv.3hCG_1586371377) by smtp.aliyun-inc.com(127.0.0.1); Thu, 09 Apr 2020 02:43:00 +0800 Subject: Re: [PATCHv2 4/8] khugepaged: Drain LRU add pagevec after swapin To: "Kirill A. Shutemov" Cc: akpm@linux-foundation.org, Andrea Arcangeli , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" References: <20200403112928.19742-1-kirill.shutemov@linux.intel.com> <20200403112928.19742-5-kirill.shutemov@linux.intel.com> <620a61ed-be87-f60e-f562-379cd3adbe08@linux.alibaba.com> <20200408130532.ktztqf5fabo3x3cd@box> From: Yang Shi Message-ID: <4b63e949-16bc-f239-89ec-93898cb4d772@linux.alibaba.com> Date: Wed, 8 Apr 2020 11:42:55 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20200408130532.ktztqf5fabo3x3cd@box> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/8/20 6:05 AM, Kirill A. Shutemov wrote: > On Mon, Apr 06, 2020 at 11:29:11AM -0700, Yang Shi wrote: >> >> On 4/3/20 4:29 AM, Kirill A. Shutemov wrote: >>> __collapse_huge_page_isolate() may fail due to extra pin in the LRU add >>> pagevec. It's petty common for swapin case: we swap in pages just to >>> fail due to the extra pin. >>> >>> Drain LRU add pagevec on sucessfull swapin. >>> >>> Signed-off-by: Kirill A. Shutemov >>> --- >>> mm/khugepaged.c | 5 +++++ >>> 1 file changed, 5 insertions(+) >>> >>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>> index fdc10ffde1ca..57ff287caf6b 100644 >>> --- a/mm/khugepaged.c >>> +++ b/mm/khugepaged.c >>> @@ -940,6 +940,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, >>> } >>> vmf.pte--; >>> pte_unmap(vmf.pte); >>> + >>> + /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ >>> + if (swapped_in) >>> + lru_add_drain(); >> There is already lru_add_drain() called in swap readahead path, please see >> swap_vma_readahead() and swap_cluster_readahead(). > But not for synchronous case. See SWP_SYNCHRONOUS_IO branch in > do_swap_page(). Aha, yes. I missed the synchronous case. > > Maybe we should drain it in swap_readpage() or in do_swap_page() after > swap_readpage()? I donno. It may be better to keep it as is. Draining lru for every page for synchronous case in do_swap_page() path sounds not very productive. Doing it in khugepaged seems acceptable. We just drain lru cache again for non-synchronous case, but the cache may be already empty so it should take very short time since nothing to drain. >