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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id ED316EB64DA for ; Mon, 10 Jul 2023 09:40:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 90F946B007B; Mon, 10 Jul 2023 05:40:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8BFAB6B007D; Mon, 10 Jul 2023 05:40:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7D5EC6B007E; Mon, 10 Jul 2023 05:40:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 6C15A6B007B for ; Mon, 10 Jul 2023 05:40:05 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 2E44C1602EC for ; Mon, 10 Jul 2023 09:40:05 +0000 (UTC) X-FDA: 80995205970.04.37B2646 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf07.hostedemail.com (Postfix) with ESMTP id 106FF40004 for ; Mon, 10 Jul 2023 09:40:02 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf07.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1688982003; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=yGosFH1ml7clbjsm/DfDtBduunSXeYaHR4Wok9XLtHQ=; b=7yfR992Hwd2pL51ga1eW3Q8b6obhREYY/fGVoNB+Ce5nCuAKszm/dNyI7Eh1w3LVL5cRcv Zb67FS+1lNkgpny86xqmqqhy8YE1PA2h8r+TX/c1Ps/DRx4MICMpqQsqo4x4KlqkTvUtPp 6U8qpa1R0cdZsljKPwlC62x7bNvDbeM= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf07.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1688982003; a=rsa-sha256; cv=none; b=y8vr4e0oCgmHforYNc2w1hb7VmA+kYN/aQn5O39sZLgqfLTXDwgdnCcSKhmwD4WNPagz5y MxdLXUtkvjbYQTCZQqtEYeeM8mcvxP2mR9WXOGYLGfgSBJImzUNaN7dsmPDrtU4eKIU9qC Tg53cou5t8pTQoHM6xwTEI1tmPA2LWI= 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 187FE2B; Mon, 10 Jul 2023 02:40:44 -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 08C693F740; Mon, 10 Jul 2023 02:39:59 -0700 (PDT) Message-ID: Date: Mon, 10 Jul 2023 10:39:58 +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> <6379dd13-551e-3c73-422a-56ce40b27deb@arm.com> <87ttucfht7.fsf@yhuang6-desk2.ccr.corp.intel.com> <878rbof8cs.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Ryan Roberts In-Reply-To: <878rbof8cs.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 106FF40004 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: srpcsrpjih8fbyo6zmguz73amnhiado1 X-HE-Tag: 1688982002-536090 X-HE-Meta: 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 EUgVZDiS qOc7N8UpQ0sX9ZcOv3NwK36jFrEUC2/mgBfqdSOOB2PqzJjQztaN3I2angVtibweLHJ+cFL9rEwyoCLX6dQOYXXbcf6y90WhBiReH8tboQXm+9zWgND7ARsvIC3swTz2TifGAryheREUYgceCpe1KhrNezvGFZ7fYHV84OKyFT6MMML+DcbUor2jmL7vMSGA5cAqs8vrxt6aegO/xvQKfxOEtBUYMouhQLw0fWcruH5Wje5ufWWACuOj6iv//VxVcjKe/WpO9MfanYOckzsmbO7HLnbEDZ8mVi7RYZt3sEekIZcIWydrTiAmRTj565iSwcZdrJcBTzYoFpmCH9S0GJ5EEAOOg61ZDoK6iXH/+SzIt6vw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/07/2023 10:01, Huang, Ying wrote: > Ryan Roberts writes: > >> On 10/07/2023 06:37, Huang, Ying wrote: >>> Ryan Roberts writes: >>> >>>> 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 for your information! "batch zap" can solve the problem. >>> >>> And, I agree with Matthew's comments to fix the large folios interaction >>> issues before merging the patches to allocate large folios as in the >>> following email. >>> >>> https://lore.kernel.org/linux-mm/ZKVdUDuwNWDUCWc5@casper.infradead.org/ >>> >>> If so, we don't need to introduce the above problem or a large patchset. >> >> I appreciate Matthew's and others position about not wanting to merge a minimal >> implementation while there are some fundamental features (e.g. compaction) it >> doesn't play well with - I'm working to create a definitive list so these items >> can be tracked and tackled. > > Good to know this, Thanks! > >> That said, I don't see this "batch zap" patch as an example of this. It's just a >> performance enhancement that improves things even further than large anon folios >> on their own. I'd rather concentrate on the core changes first then deal with >> this type of thing later. Does that work for you? > > IIUC, allocating large folios upon page fault depends on splitting large > folios in page_remove_rmap() to avoid memory wastage. Splitting large > folios in page_remove_rmap() depends on "batch zap" to avoid performance > regression in zap_pte_range(). So we need them to be done earlier. Or > I miss something? My point was just that large anon folios improves performance significantly overall, despite a small perf regression in zap_pte_range(). That regression is reduced further by a patch from Yin Fengwei to reduce the lock contention [1]. So it doesn't seem urgent to me to get the "batch zap" change in. I'll add it to my list, then prioritize it against the other stuff. [1] https://lore.kernel.org/linux-mm/20230429082759.1600796-1-fengwei.yin@intel.com/ > > Best Regards, > Huang, Ying