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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C9CF3E9A03B for ; Wed, 18 Feb 2026 04:50:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C9A576B0088; Tue, 17 Feb 2026 23:50:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C481B6B0089; Tue, 17 Feb 2026 23:50:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B4A716B008A; Tue, 17 Feb 2026 23:50:32 -0500 (EST) 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 9E4C96B0088 for ; Tue, 17 Feb 2026 23:50:32 -0500 (EST) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 3462A1C438 for ; 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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1771390230; 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=QRKLmVWmeBE1n35RnPgSettqMdTarJ3x0ofKR0Onz9c=; b=GJG2ysUKf1tlFRYwLSRLlRadaH6gr6FbnTOYVfvlKQMXVAMLI30TP9/qjpWvFYlkd2EEhE 5SxjbIrUSsnHhmdfbwkLu6TtJlSjT0aAgvx69MKHOSEjbOhnjZ1LHWJZUpHW/V+5CueQvP QMdtEzxtPTKc3DVNENF2b5+UMdS3Z5w= 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 917C41477; Tue, 17 Feb 2026 20:50:22 -0800 (PST) Received: from [10.164.19.71] (unknown [10.164.19.71]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B4E3B3F7F5; Tue, 17 Feb 2026 20:50:25 -0800 (PST) Message-ID: Date: Wed, 18 Feb 2026 10:20:22 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [REGRESSION] mm/mprotect: 2x+ slowdown for >=400KiB regions since PTE batching (cac1db8c3aad) To: Luke Yang Cc: pfalcato@suse.de, david@kernel.org, surenb@google.com, jhladky@redhat.com, akpm@linux-foundation.org, Liam.Howlett@oracle.com, willy@infradead.org, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <764792ea-6029-41d8-b079-5297ca62505a@kernel.org> <71fbee21-f1b4-4202-a790-5076850d8d00@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 1C40B18000F X-Stat-Signature: buftai6djyf5ip81m1ku8g3d65fghs7w X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1771390229-27850 X-HE-Meta: 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 ZTAopGw3 hBMSlgUWblRjSReGyF8hF+QGw43NzPhMCM+/vOm2o1N+SBRLKH8yvm0RR2MrxjyJGIbuS48/w8SGjafBBHG/PbLGzxUJGlTq5HU6iPqV5d6f5bnPNp4B/uFwfzoihXk+sarEqZ3OfOVfk74ByuP4zu+yIHaAhLYAlEqmgIBQ6H8F5/KKDRnL7PAsGWXkZbkbuyIK6 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 17/02/26 11:13 pm, Luke Yang wrote: > On Mon, Feb 16, 2026 at 03:42:08PM +0530, Dev Jain wrote: >> On 13/02/26 10:56 pm, David Hildenbrand (Arm) wrote: >>> On 2/13/26 18:16, Suren Baghdasaryan wrote: >>>> On Fri, Feb 13, 2026 at 4:24 PM Pedro Falcato wrote: >>>>> On Fri, Feb 13, 2026 at 04:47:29PM +0100, David Hildenbrand (Arm) wrote: >>>>>> Hi! >>>>>> >>>>>> >>>>>> Micro-benchmark results are nice. But what is the real word impact? >>>>>> IOW, why >>>>>> should we care? >>>>> Well, mprotect is widely used in thread spawning, code JITting, >>>>> and even process startup. And we don't want to pay for a feature we can't >>>>> even use (on x86). >>>> I agree. When I straced Android's zygote a while ago, mprotect() came >>>> up #30 in the list of most frequently used syscalls and one of the >>>> most used mm-related syscalls due to its use during process creation. >>>> However, I don't know how often it's used on VMAs of size >=400KiB. >>> See my point? :) If this is apparently so widespread then finding a real >>> reproducer is likely not a problem. Otherwise it's just speculation. >>> >>> It would also be interesting to know whether the reproducer ran with any >>> sort of mTHP enabled or not.  >> Yes. Luke, can you experiment with the following microbenchmark: >> >> https://pastebin.com/3hNtYirT >> >> and see if there is an optimization for pte-mapped 2M folios, before and >> after the commit? >> >> (set transparent_hugepages/enabled=always, hugepages-2048Kb/enabled=always) > ---------- > amd-epyc2-rome > > # before commit > $ uname -r > 6.16.0-65.eln150.x86_64 > # after commit > $ uname -r > 6.17.0-0.rc1.17.eln150.x86_64 > > $ cat /sys/kernel/mm/transparent_hugepage/enabled > [always] madvise never > > $ cat /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled > [always] inherit madvise never > > Before commit: Total = 6895988972 > After commit: Total = 2303697782 > Percentage change: -66.6% > > ---------- > amd-epyc3-milanx > > # before commit > $ uname -r > 6.16.0-65.eln150.x86_64 > # after commit > $ uname -r > 6.17.0-0.rc1.17.eln150.x86_64 > > $ cat /sys/kernel/mm/transparent_hugepage/enabled > [always] madvise never > > $ cat /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled > [always] inherit madvise never > > Before commit: Total = 4006750392 > After commit: Total = 1497733191 > Percentage change: -62.6% > ---------- Thanks. So after all, batching improves stuff :) > > Luke >