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 5B8D8EB64D9 for ; Tue, 4 Jul 2023 13:23:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CD9FD28007A; Tue, 4 Jul 2023 09:23:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C8B80280076; Tue, 4 Jul 2023 09:23:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B51BE28007A; Tue, 4 Jul 2023 09:23:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id A15C9280076 for ; Tue, 4 Jul 2023 09:23:26 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 6205BC0A35 for ; Tue, 4 Jul 2023 13:23:26 +0000 (UTC) X-FDA: 80973996012.27.E46DB3C Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf22.hostedemail.com (Postfix) with ESMTP id 9049AC0009 for ; Tue, 4 Jul 2023 13:23:24 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=none; spf=pass (imf22.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1688477004; 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=GzTBDobSOc0TvfU0N2f9fXFPww50cmXhIi5A5EXimcQ=; b=WggSArdQG1QSVk8N9s9m66QT4tKTYJ1IGIQtXpQUO2fDMjzOqKsVnrt8qWtzfWl/t4ydWG NADASQES65h0vmIkfRJO9K8EOicylNDUNu/CG5nLKS77cELM0VKfZ1081i0hzbqMqfPMum tcNCD1vPGBGqikEp5KU8wdRK2sxJJ5A= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1688477004; a=rsa-sha256; cv=none; b=C1tERr7znM2Vigcce5WNCaVpW2b7eWW3IHe9yQV4u81br5w8r3+NlhdpGLN2FxImdNZtHw 3Ca1EGaLCijelym7U+OiKJanrK2TUEU4A56bDyHkaTR/+dmFBRlMuqnVlrHXkktqDBUDWN YfWYy0enHW0OoVVLDiwcD06hfLVVAl4= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=none; spf=pass (imf22.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com 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 F175D1474; Tue, 4 Jul 2023 06:24:05 -0700 (PDT) Received: from [10.1.35.40] (C02Z41KALVDN.cambridge.arm.com [10.1.35.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E8B323F663; Tue, 4 Jul 2023 06:23:21 -0700 (PDT) Message-ID: Date: Tue, 4 Jul 2023 14:23:20 +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 3/5] mm: Default implementation of arch_wants_pte_order() From: Ryan Roberts To: Yu Zhao , "Yin, Fengwei" Cc: Andrew Morton , Matthew Wilcox , "Kirill A. Shutemov" , David Hildenbrand , 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> <20230703135330.1865927-4-ryan.roberts@arm.com> <6d389825-1fc0-5c16-7858-2290fd632682@arm.com> In-Reply-To: <6d389825-1fc0-5c16-7858-2290fd632682@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: x5ytratb3ndj6k1oh4bgbwuxasagce86 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 9049AC0009 X-Rspam-User: X-HE-Tag: 1688477004-433947 X-HE-Meta: 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 4AwDWWtJ ZoDv+sH9eKLlBSLr2BrFtTtgFj7u/rp30MBZt04K6wKBFzUiDR5x0y8fR/Aj9YttMmyrYJhwWvlutHbR+EtMG52zfQVanVL5YbnpYLguQL99LAsi4qR0vd5towj0mLhHXDbJ4l0IDETpOr1Goe05T2mu647rcIcgnm9oCdGWUYjhxNAQ0+O0cp78YUQenwgVNtsjpmsXEqTE6XSEvGoXrHNwgAEENBpJYOggODQYqaaMiwsGYDyDBoaCc08PCQNwWQgBqwUgNMy+Rxec= 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 04/07/2023 13:36, Ryan Roberts wrote: > On 04/07/2023 04:59, Yu Zhao wrote: >> On Mon, Jul 3, 2023 at 9:02 PM Yu Zhao wrote: >>> >>> On Mon, Jul 3, 2023 at 8:23 PM Yin, Fengwei wrote: >>>> >>>> >>>> >>>> On 7/3/2023 9:53 PM, Ryan Roberts wrote: >>>>> arch_wants_pte_order() can be overridden by the arch to return the >>>>> preferred folio order for pte-mapped memory. This is useful as some >>>>> architectures (e.g. arm64) can coalesce TLB entries when the physical >>>>> memory is suitably contiguous. >>>>> >>>>> The first user for this hint will be FLEXIBLE_THP, which aims to >>>>> allocate large folios for anonymous memory to reduce page faults and >>>>> other per-page operation costs. >>>>> >>>>> Here we add the default implementation of the function, used when the >>>>> architecture does not define it, which returns the order corresponding >>>>> to 64K. >>>>> >>>>> Signed-off-by: Ryan Roberts >>>>> --- >>>>> include/linux/pgtable.h | 13 +++++++++++++ >>>>> 1 file changed, 13 insertions(+) >>>>> >>>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>>>> index a661a17173fa..f7e38598f20b 100644 >>>>> --- a/include/linux/pgtable.h >>>>> +++ b/include/linux/pgtable.h >>>>> @@ -13,6 +13,7 @@ >>>>> #include >>>>> #include >>>>> #include >>>>> +#include >>>>> >>>>> #if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLDED) - \ >>>>> defined(__PAGETABLE_PMD_FOLDED) != CONFIG_PGTABLE_LEVELS >>>>> @@ -336,6 +337,18 @@ static inline bool arch_has_hw_pte_young(void) >>>>> } >>>>> #endif >>>>> >>>>> +#ifndef arch_wants_pte_order >>>>> +/* >>>>> + * Returns preferred folio order for pte-mapped memory. Must be in range [0, >>>>> + * PMD_SHIFT-PAGE_SHIFT) and must not be order-1 since THP requires large folios >>>>> + * to be at least order-2. >>>>> + */ >>>>> +static inline int arch_wants_pte_order(struct vm_area_struct *vma) >>>>> +{ >>>>> + return ilog2(SZ_64K >> PAGE_SHIFT); >>>> Default value which is not related with any silicon may be: PAGE_ALLOC_COSTLY_ORDER? >>>> >>>> Also, current pcp list support cache page with order 0...PAGE_ALLOC_COSTLY_ORDER, 9. >>>> If the pcp could cover the page, the pressure to zone lock will be reduced by pcp. >>> >>> The value of PAGE_ALLOC_COSTLY_ORDER is reasonable but again it's a >>> s/w policy not a h/w preference. Besides, I don't think we can include >>> mmzone.h in pgtable.h. >> >> I think we can make a compromise: >> 1. change the default implementation of arch_has_hw_pte_young() to return 0, and >> 2. in memory.c, we can try PAGE_ALLOC_COSTLY_ORDER for archs that >> don't override arch_has_hw_pte_young(), or if its return value is too >> large to fit. >> This should also take care of the regression, right? > > I think you are suggesting that we use 0 as a sentinel which we then translate > to PAGE_ALLOC_COSTLY_ORDER? I already have a max_anon_folio_order() function in > memory.c (actually it is currently a macro defined as arch_wants_pte_order()). > > So it would become (I'll talk about the vma concern separately in the thread > where you raised it): > > static inline int max_anon_folio_order(struct vm_area_struct *vma) > { > int order = arch_wants_pte_order(vma); > > return order ? order : PAGE_ALLOC_COSTLY_ORDER; > } > > Correct? Actually, I'm not sure its a good idea to default to a fixed order. If running on an arch with big base pages (e.g. powerpc with 64K pages?), that will soon add up to a big chunk of memory, which could be wasteful? PAGE_ALLOC_COSTLY_ORDER = 3 so with 64K base page, that 512K. Is that a concern? Wouldn't it be better to define this as an absolute size? Or even the min of PAGE_ALLOC_COSTLY_ORDER and an absolute size? > > I don't see how it fixes the regression (assume you're talking about > Speedometer) though? On arm64 arch_wants_pte_order() will still be returning > order-4. >