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 56AB9C6FA99 for ; Fri, 10 Mar 2023 11:25:48 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7C5F76B0072; Fri, 10 Mar 2023 06:25:47 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 775C96B0074; Fri, 10 Mar 2023 06:25:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 617BB6B0075; Fri, 10 Mar 2023 06:25:47 -0500 (EST) 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 4DC046B0072 for ; Fri, 10 Mar 2023 06:25:47 -0500 (EST) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 1118141220 for ; Fri, 10 Mar 2023 11:25:47 +0000 (UTC) X-FDA: 80552758734.27.0AD636E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf13.hostedemail.com (Postfix) with ESMTP id 6C2A02001B for ; Fri, 10 Mar 2023 11:25:43 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Z2OvGRel; spf=pass (imf13.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1678447545; 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:dkim-signature; bh=Wnd+07RC7REbUFCKV/Th3JnGXK55wayqDQMn9UZgDc0=; b=I9kb8SI0DQk7XWMZIz06zxdko3RhbniCj9c55ir4BLIHae4zhVFwaUoJRhoEtqVfkPFk69 0rs+sLrpWmTAvHeJqrbOBP/38q7MPm4ioMOa9VZdzM7bXmmNQADmCBomSh4kyqbbUyl69W HaGD2iiQpwedCrqyowcLTsSi4nBEFvE= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Z2OvGRel; spf=pass (imf13.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1678447545; a=rsa-sha256; cv=none; b=o08WPdOSUmGMiNSO/dBEl9nl721S3Esa4HGLlvX5/2fjjQqgPFcn1FXthdgkq1m+1tqFhD 44feKPVKlUgBQNYaKdJzVnVEnXV0Z4Ew6mULpR05aJM1HHf2dDwlVu0+52Udnnjw6Yt6lO JncM+Do8EHiDeo0orAJbPT0RS/fQsck= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1678447542; h=from:from: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=Wnd+07RC7REbUFCKV/Th3JnGXK55wayqDQMn9UZgDc0=; b=Z2OvGRelR1YkZanx+Rl8dB69GDgZx12PFtJusProLTU6g5w+8ejV4kku28K8jkkidrZGKf IAW8ETrJ6NlYVCliCphOPQwJonm0bHW9pZzwgpOdpckeTSCv3x2/wi8jMw6cycgvnZGx2n s2tsnTi6owLz3bXWl/rDfTygm7qIp4Y= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-412-VTvyO7fwPsOrxn2Ox_aF1g-1; Fri, 10 Mar 2023 06:25:41 -0500 X-MC-Unique: VTvyO7fwPsOrxn2Ox_aF1g-1 Received: by mail-wm1-f70.google.com with SMTP id z6-20020a05600c220600b003e222c9c5f4so1688796wml.4 for ; Fri, 10 Mar 2023 03:25:40 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678447540; h=content-transfer-encoding:in-reply-to:organization:from:references :cc:to:content-language:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Wnd+07RC7REbUFCKV/Th3JnGXK55wayqDQMn9UZgDc0=; b=F/bD1wgigYZHC80BLTYg9JICBK6p2BUs+WnbHHrtoZ5bghDfHocqNGh/ataOAtAJQ6 PwGwyyWXHlilV0UW+F0nbtGQHvRgnrsgCEL6P4BNFUCZajzS0srFeDMOmKUSSe9k7vCg 6FvwyLuFXI3xNdzwUR94gcyfL6dE+KRTA16Gvnz6QSMBe1UQhpTlej2jpFkPwPrK0vxX vPLLiNt1A8ciWyDcTpH7hMhZgeREiX75e9VtXSTDPs4dEN4MW/cH/rXPVJl7U1/8LmYb jKL+0St1uWQC14vfAYoC3cNoXKAm68VJ7y7cMurFgKuxRX//zOJhQBc/EGV0ko9afZ2Z nqKw== X-Gm-Message-State: AO0yUKXHW89PKlZhCMlKuDFozCyUnj/Pk0DMyt/fRiDMfxOrXFRF0y6j kJ6KMzKNeA3jbWOOlBcpJZ6KNrrPfSNNC7G9hZlTmhdqh0/9w70Nya9m3rfjAo4+eftEdkNflXb 9yjYdiYyiby8= X-Received: by 2002:a05:600c:1c18:b0:3eb:40de:9838 with SMTP id j24-20020a05600c1c1800b003eb40de9838mr1493791wms.7.1678447540112; Fri, 10 Mar 2023 03:25:40 -0800 (PST) X-Google-Smtp-Source: AK7set9Gs81tceVs9wUO6S04OgBq58QF0bgNdk/WOJfvkRngarnjh92tvKWEeNaXnZ8S9MvTf4e2sg== X-Received: by 2002:a05:600c:1c18:b0:3eb:40de:9838 with SMTP id j24-20020a05600c1c1800b003eb40de9838mr1493775wms.7.1678447539807; Fri, 10 Mar 2023 03:25:39 -0800 (PST) Received: from ?IPV6:2003:cb:c707:1100:12e6:ffa5:775d:18ee? (p200300cbc707110012e6ffa5775d18ee.dip0.t-ipconnect.de. [2003:cb:c707:1100:12e6:ffa5:775d:18ee]) by smtp.gmail.com with ESMTPSA id f21-20020a7bcc15000000b003e20a6fd604sm1812910wmh.4.2023.03.10.03.25.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Mar 2023 03:25:39 -0800 (PST) Message-ID: <9f44de08-b484-baa7-80c8-0a02a7abb717@redhat.com> Date: Fri, 10 Mar 2023 12:25:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: THP backed thread stacks To: William Kucharski , Zach O'Keefe Cc: Mike Kravetz , Peter Xu , Rik van Riel , Mike Rapoport , Linux-MM , LKML References: <20230306235730.GA31451@monkey> <20230307004049.GC4956@monkey> <20230308190206.GA4005@monkey> <20230309233340.GC3700@monkey> <9F855331-33B2-4366-9375-988B0D3DAC98@oracle.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <9F855331-33B2-4366-9375-988B0D3DAC98@oracle.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6C2A02001B X-Stat-Signature: augbci1zggoqt6ynkrod7ac9jij94j3t X-Rspam-User: X-HE-Tag: 1678447543-889812 X-HE-Meta: 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 5few82rv cbFSrxeIzRvF6Ruvue0s6C3K+w7PdYXZ565+4xF6Uk4upUNyVcWRn7EACVxLbDT0Yla3ArO2OzpxvKNNSOWp5bqQ2UR0zkF2kk1W5vvk48xShHjkeenR8Z1O/j4gPUMSXZnxnJXsY0fm8Imxp5kpLngifLf28STaIHK0/CtpXhfgxmZk2U1q4LcbEOKIlhisF/KJwYON357KLztdJUt1NnJvAqBzBxI+5b+BXKa4Hnm77BCxWHa4nekcds71oQJQFwwQ3rj9gWVJqutyYLZ27u8Z2BkEz0bR3zmRQpxWswBZlcNOCtB/rEYALXaBvxJOLqvmFQmuQ8B9xctjsNxguDVqlgHNkeIcBlrL267r7uPeMiYbbZwTzR1pEpWD0jCUjf7e0dWZhWdOX7HUtT37W8XNiuqjF0AFAQ7z5EtVp/rVF+hY= 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 10.03.23 02:40, William Kucharski wrote: > > >> On Mar 9, 2023, at 17:05, Zach O'Keefe wrote: >> >>> I think the hugepage alignment in their environment was somewhat luck. >>> One suggestion made was to change stack size to avoid alignment and >>> hugepage usage. That 'works' but seems kind of hackish. >> >> That was my first thought, if the alignment was purely due to luck, >> and not somebody manually specifying it. Agreed it's kind of hackish >> if anyone can get bit by this by sheer luck. > > I don't agree it's "hackish" at all, but I go more into that below. > >> >>> Also, David H pointed out the somewhat recent commit to align sufficiently >>> large mappings to THP boundaries. This is going to make all stacks huge >>> page aligned. >> >> I think that change was reverted by Linus in commit 0ba09b173387 >> ("Revert "mm: align larger anonymous mappings on THP boundaries""), >> until it's perf regressions were better understood -- and I haven't >> seen a revamp of it. > > It's too bad it was reverted, though I understand the concerns regarding it. > > From my point of view, if an address is properly aligned and a caller is > asking for 2M+ to be mapped, it's going to be advantageous from a purely > system-focused point of view to do that mapping with a THP. Just noting that, if user space requests multiple smaller mappings, and the kernel decides to all place them in the same PMD, all VMAs might get merged and you end up with a properly aligned VMA where khugepaged would happily place a THP. That case is, of course, different to the "user space asks for 2M+" mapping case, but from khugepaged perspective they might look alike -- and it might be unclear if a THP is valuable or not (IOW maybe that THP could be better used somewhere else). -- Thanks, David / dhildenb