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 620BBC4332F for ; Wed, 1 Nov 2023 14:03:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D03978D0067; Wed, 1 Nov 2023 10:03:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CB2AF8D0001; Wed, 1 Nov 2023 10:03:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B2C028D0067; Wed, 1 Nov 2023 10:03:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 9CC3B8D0001 for ; Wed, 1 Nov 2023 10:03:39 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 6F9A3B5F59 for ; Wed, 1 Nov 2023 14:03:39 +0000 (UTC) X-FDA: 81409553358.23.0B17798 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf21.hostedemail.com (Postfix) with ESMTP id 9E0E81C01DE for ; Wed, 1 Nov 2023 14:02:53 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=none; spf=pass (imf21.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-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1698847374; a=rsa-sha256; cv=none; b=dRwE8DuOtlQerCfIkGDfMqawDQVDa9uzE7Xob8XdFYM7F+UqfQfMa+SWCJBzRJIasC6qSS 7opQueURoDjZBPlkCH/PQ69vEZ3AvuXkZGQI2FIlHiU2wVO1ZxJd9hHZKbuKTOrAlCMCll NJUFf9CVl7/00b2sM6e/Ru9qa1nauNo= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=none; spf=pass (imf21.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=1698847374; 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=PgajSDezgWkUCB6FYm0cwlq8vJuyIsYx72LXciZLKl8=; b=Nj26tdU/r+td9j+AsDJegsM7fveZ5swil7YFR/QVUfnszHraai7MWsY01/tXprpkIlEDjR wgJyFix1LbqZXRebyzNo9JBzBIMQ3SL6C5lJ3SOwrM32TvTGR+B9S4CPN/Ipd4/bvc0ILa nMQ/mn++RJ12c4DwLgqL+BpEKjefKaA= 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 3A3852F4; Wed, 1 Nov 2023 07:03:34 -0700 (PDT) Received: from [10.1.34.131] (XHFQ2J9959.cambridge.arm.com [10.1.34.131]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 143943F64C; Wed, 1 Nov 2023 07:02:49 -0700 (PDT) Message-ID: <148676a4-8267-42de-a3ad-a3734e3f4bd9@arm.com> Date: Wed, 1 Nov 2023 14:02:48 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 0/9] variable-order, large folios for anonymous memory Content-Language: en-GB To: Yang Shi Cc: David Hildenbrand , Andrew Morton , Matthew Wilcox , Yin Fengwei , Yu Zhao , Catalin Marinas , Anshuman Khandual , "Huang, Ying" , Zi Yan , Luis Chamberlain , Itaru Kitayama , "Kirill A. Shutemov" , John Hubbard , David Rientjes , Vlastimil Babka , Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20230929114421.3761121-1-ryan.roberts@arm.com> <6d89fdc9-ef55-d44e-bf12-fafff318aef8@redhat.com> <7a3a2d49-528d-4297-ae19-56aa9e6c59c6@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 9E0E81C01DE X-Stat-Signature: i1mghe86p6fm8wpyyxt6sibhgemu4n8e X-HE-Tag: 1698847373-7992 X-HE-Meta: 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 v/0oZQ0T n8kUKZKE9HtHrkNHvPvydShD8zh0ykVLnWDuakQyoUfyDuBhkaLe8hmOB2RMBMg/8NSxFKA1avl6ENkxLzxV+N9aBYIw7jaw7zWAMlXNSazrGQUlg/+Oibz1zKfS5fYVFGvee5fqGh/r/oZFX5+MHNRJgEiXVJnDUiu3jph7odW+x6Ivg86XV5cbDzbk8VNIVAdbNqGYmW6/LWlVfVCrpJKeuHl6otOEgiwD1UaYcwYt04Sk9FJu9K0qlFQ1g24TDXZDwf2g4ktxnQarITa69pDViKQ== 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: List-Subscribe: List-Unsubscribe: On 31/10/2023 18:29, Yang Shi wrote: > On Tue, Oct 31, 2023 at 4:55 AM Ryan Roberts wrote: >> >> On 31/10/2023 11:50, Ryan Roberts wrote: >>> On 06/10/2023 21:06, David Hildenbrand wrote: >>> [...] >>>> >>>> Change 2: sysfs interface. >>>> >>>> If we call it THP, it shall go under "/sys/kernel/mm/transparent_hugepage/", I >>>> agree. >>>> >>>> What we expose there and how, is TBD. Again, not a friend of "orders" and >>>> bitmaps at all. We can do better if we want to go down that path. >>>> >>>> Maybe we should take a look at hugetlb, and how they added support for multiple >>>> sizes. What *might* make sense could be (depending on which values we actually >>>> support!) >>>> >>>> >>>> /sys/kernel/mm/transparent_hugepage/hugepages-64kB/ >>>> /sys/kernel/mm/transparent_hugepage/hugepages-128kB/ >>>> /sys/kernel/mm/transparent_hugepage/hugepages-256kB/ >>>> /sys/kernel/mm/transparent_hugepage/hugepages-512kB/ >>>> /sys/kernel/mm/transparent_hugepage/hugepages-1024kB/ >>>> /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/ >>>> >>>> Each one would contain an "enabled" and "defrag" file. We want something minimal >>>> first? Start with the "enabled" option. >>>> >>>> >>>> enabled: always [global] madvise never >>>> >>>> Initially, we would set it for PMD-sized THP to "global" and for everything else >>>> to "never". >>> >>> Hi David, >>> >>> I've just started coding this, and it occurs to me that I might need a small >>> clarification here; the existing global "enabled" control is used to drive >>> decisions for both anonymous memory and (non-shmem) file-backed memory. But the >>> proposed new per-size "enabled" is implicitly only controlling anon memory (for >>> now). >>> >>> 1) Is this potentially confusing for the user? Should we rename the per-size >>> controls to "anon_enabled"? Or is it preferable to jsut keep it vague for now so >>> we can reuse the same control for file-backed memory in future? >>> >>> 2) The global control will continue to drive the file-backed memory decision >>> (for now), even when hugepages-2048kB/enabled != "global"; agreed? >>> >>> Thanks, >>> Ryan >>> >> >> Also, an implementation question: >> >> hugepage_vma_check() doesn't currently care whether enabled="never" for DAX VMAs >> (although it does honour MADV_NOHUGEPAGE and the prctl); It will return true >> regardless. Is that by design? It couldn't fathom any reasoning from the commit log: > > The enabled="never" is for anonymous VMAs, DAX VMAs are typically file VMAs. That's not quite true; enabled="never" is honoured for non-DAX/non-shmem file VMAs (for collapse via CONFIG_READ_ONLY_THP_FOR_FS and more recently for anything that implements huge_fault() - see 7a81751fcdeb833acc858e59082688e3020bfe12).