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 058E5EB64DA for ; Fri, 7 Jul 2023 09:42:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232747AbjGGJme (ORCPT ); Fri, 7 Jul 2023 05:42:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55756 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232215AbjGGJmb (ORCPT ); Fri, 7 Jul 2023 05:42:31 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 830AAFF for ; Fri, 7 Jul 2023 02:42:30 -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 330EFD75; Fri, 7 Jul 2023 02:43:12 -0700 (PDT) Received: from [10.57.77.63] (unknown [10.57.77.63]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 04D283F73F; Fri, 7 Jul 2023 02:42:27 -0700 (PDT) Message-ID: <6379dd13-551e-3c73-422a-56ce40b27deb@arm.com> Date: Fri, 7 Jul 2023 10:42:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v2 2/5] mm: Allow deferred splitting of arbitrary large anon folios To: "Huang, Ying" Cc: Andrew Morton , Matthew Wilcox , "Kirill A. Shutemov" , Yin Fengwei , David Hildenbrand , Yu Zhao , Catalin Marinas , Will Deacon , Anshuman Khandual , Yang Shi , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20230703135330.1865927-1-ryan.roberts@arm.com> <20230703135330.1865927-3-ryan.roberts@arm.com> <877crcgmj1.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Ryan Roberts In-Reply-To: <877crcgmj1.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Somehow I managed to reply only to the linux-arm-kernel list on first attempt so resending: On 07/07/2023 09:21, Huang, Ying wrote: > Ryan Roberts writes: > >> With 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 82ef5ba363d1..bbcb2308a1c5 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1474,7 +1474,7 @@ 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); >> } > > One possible issue is that even for large folios mapped only in one > process, in zap_pte_range(), we will always call deferred_split_folio() > unnecessarily before freeing a large folio. Hi Huang, thanks for reviewing! I have a patch that solves this problem by determining a range of ptes covered by a single folio and doing a "batch zap". This prevents the need to add the folio to the deferred split queue, only to remove it again shortly afterwards. This reduces lock contention and I can measure a performance improvement for the kernel compilation benchmark. See [1]. However, I decided to remove it from this patch set on Yu Zhao's advice. We are aiming for the minimal patch set to start with and wanted to focus people on that. I intend to submit it separately later on. [1] https://lore.kernel.org/linux-mm/20230626171430.3167004-8-ryan.roberts@arm.com/ Thanks, Ryan > > Best Regards, > Huang, Ying > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel