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=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 54C87C433DF for ; Tue, 11 Aug 2020 01:52:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 30CF920716 for ; Tue, 11 Aug 2020 01:52:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="INWLARXj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728182AbgHKBwA (ORCPT ); Mon, 10 Aug 2020 21:52:00 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:30437 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727848AbgHKBv7 (ORCPT ); Mon, 10 Aug 2020 21:51:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597110718; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=B65NjOD6ipSRjE7zhOhhykThhsv5n+dkos2I3Rfjbvw=; b=INWLARXjig+umfzMpo3V+DJTYBByRhIGjfg2wNkHk7/+6ISdDHn6VjdS3UW1UOgVNPb8mc xmfkvViRo4V1NajOzcTL8N1P6oUDieV0d1zgWQoKv2mgmkXCJNHdPPXmbOYjGSmVU1OT0r RiqWlhCfkZjA2f8RQ8T45thNbXFbYNg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-155-TQViRskyOaipOO4uc-UJCg-1; Mon, 10 Aug 2020 21:51:54 -0400 X-MC-Unique: TQViRskyOaipOO4uc-UJCg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E1E898014D7; Tue, 11 Aug 2020 01:51:52 +0000 (UTC) Received: from localhost (ovpn-13-96.pek2.redhat.com [10.72.13.96]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 000926111F; Tue, 11 Aug 2020 01:51:51 +0000 (UTC) Date: Tue, 11 Aug 2020 09:51:48 +0800 From: Baoquan He To: Mike Kravetz Cc: Wei Yang , mhocko@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 10/10] mm/hugetlb: not necessary to abuse temporary page to workaround the nasty free_huge_page Message-ID: <20200811015148.GA10792@MiWiFi-R3L-srv> References: <20200807091251.12129-1-richard.weiyang@linux.alibaba.com> <20200807091251.12129-11-richard.weiyang@linux.alibaba.com> <20200810021737.GV14854@MiWiFi-R3L-srv> <129cc03e-c6d5-24f8-2f3c-f5a3cc821e76@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <129cc03e-c6d5-24f8-2f3c-f5a3cc821e76@oracle.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/10/20 at 05:19pm, Mike Kravetz wrote: > On 8/9/20 7:17 PM, Baoquan He wrote: > > On 08/07/20 at 05:12pm, Wei Yang wrote: > >> Let's always increase surplus_huge_pages and so that free_huge_page > >> could decrease it at free time. > >> > >> Signed-off-by: Wei Yang > >> --- > >> mm/hugetlb.c | 14 ++++++-------- > >> 1 file changed, 6 insertions(+), 8 deletions(-) > >> > >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c > >> index 1f2010c9dd8d..a0eb81e0e4c5 100644 > >> --- a/mm/hugetlb.c > >> +++ b/mm/hugetlb.c > >> @@ -1913,21 +1913,19 @@ static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask, > >> return NULL; > >> > >> spin_lock(&hugetlb_lock); > >> + > >> + h->surplus_huge_pages++; > >> + h->surplus_huge_pages_node[page_to_nid(page)]++; > >> + > >> /* > >> * We could have raced with the pool size change. > >> * Double check that and simply deallocate the new page > >> - * if we would end up overcommiting the surpluses. Abuse > >> - * temporary page to workaround the nasty free_huge_page > >> - * codeflow > >> + * if we would end up overcommiting the surpluses. > >> */ > >> - if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) { > >> - SetPageHugeTemporary(page); > > > > Hmm, the temporary page way is taken intentionally in > > commit 9980d744a0428 ("mm, hugetlb: get rid of surplus page accounting tricks"). > > From code, this is done inside hugetlb_lock holding, and the code flow > > is straightforward, should be safe. Adding Michal to CC. > > > > I remember when the temporary page code was added for page migration. > The use of temporary page here was added at about the same time. Temporary > page does have one advantage in that it will not CAUSE surplus count to > exceed overcommit. This patch could cause surplus to exceed overcommit > for a very short period of time. However, do note that for this to happen > the code needs to race with a pool resize which itself could cause surplus > to exceed overcommit. > > IMO both approaches are valid. > - Advantage of temporary page is that it can not cause surplus to exceed > overcommit. Disadvantage is as mentioned in the comment 'abuse of temporary > page'. > - Advantage of this patch is that it uses existing counters. Disadvantage > is that it can momentarily cause surplus to exceed overcommit. Yeah, since it's all done inside hugetlb_lock, should be OK even though it may cause surplus to exceed overcommit. > > Unless someone has a strong opinion, I prefer the changes in this patch. Agree, I also prefer the code change in this patch, to remove the unnecessary confusion about the temporary page.