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 9FCC5EB64DC for ; Mon, 17 Jul 2023 16:01:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231547AbjGQQBb (ORCPT ); Mon, 17 Jul 2023 12:01:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53404 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229528AbjGQQB3 (ORCPT ); Mon, 17 Jul 2023 12:01:29 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1BEB0D8 for ; Mon, 17 Jul 2023 09:01:28 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3B95DC15; Mon, 17 Jul 2023 09:02:11 -0700 (PDT) Received: from [10.57.76.30] (unknown [10.57.76.30]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 02C8C3F738; Mon, 17 Jul 2023 09:01:24 -0700 (PDT) Message-ID: <028c5f5b-b67c-9ccc-bc06-468f47362999@arm.com> Date: Mon, 17 Jul 2023 17:01:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v1 1/3] mm: Allow deferred splitting of arbitrary large anon folios To: David Hildenbrand , Andrew Morton , Matthew Wilcox , Yin Fengwei , Yu Zhao , Yang Shi , "Huang, Ying" , Zi Yan Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20230717143110.260162-1-ryan.roberts@arm.com> <20230717143110.260162-2-ryan.roberts@arm.com> <90b406af-9db4-b668-a7a0-e574e104c84c@redhat.com> From: Ryan Roberts In-Reply-To: <90b406af-9db4-b668-a7a0-e574e104c84c@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/07/2023 16:42, David Hildenbrand wrote: > On 17.07.23 16:31, Ryan Roberts wrote: >> In preparation for the introduction of large folios for anonymous >> memory, we would like to be able to split them when they have unmapped >> subpages, in order to free those unused pages under memory pressure. So >> remove the artificial requirement that the large folio needed to be at >> least PMD-sized. >> >> Signed-off-by: Ryan Roberts >> Reviewed-by: Yu Zhao >> Reviewed-by: Yin Fengwei >> --- >>   mm/rmap.c | 2 +- >>   1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 0c0d8857dfce..2baf57d65c23 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1430,7 +1430,7 @@ void page_remove_rmap(struct page *page, struct >> vm_area_struct *vma, >>            * page of the folio is unmapped and at least one page >>            * is still mapped. >>            */ >> -        if (folio_test_pmd_mappable(folio) && folio_test_anon(folio)) >> +        if (folio_test_large(folio) && folio_test_anon(folio)) >>               if (!compound || nr < nr_pmdmapped) >>                   deferred_split_folio(folio); > > !compound will always be true I guess, so nr_pmdmapped == 0 (which will always > be the case) will be ignored. I don't follow why !compound will always be true. This function is page_remove_rmap() (not folio_remove_rmap_range() which I add in a later patch). page_remove_rmap() can work on pmd-mapped pages where compound=true is passed in. > > Reviewed-by: David Hildenbrand >