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 42F58EE57FA for ; Wed, 31 Dec 2025 09:53:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 792FD6B0088; Wed, 31 Dec 2025 04:53:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 7166D6B0089; Wed, 31 Dec 2025 04:53:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 622726B008A; Wed, 31 Dec 2025 04:53:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 524E46B0088 for ; Wed, 31 Dec 2025 04:53:12 -0500 (EST) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D095FC2C93 for ; Wed, 31 Dec 2025 09:53:11 +0000 (UTC) X-FDA: 84279302982.08.0DEF3EB Received: from out-172.mta1.migadu.com (out-172.mta1.migadu.com [95.215.58.172]) by imf20.hostedemail.com (Postfix) with ESMTP id D7CE51C0003 for ; Wed, 31 Dec 2025 09:53:09 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=kA0qCy5s; spf=pass (imf20.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.172 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1767174790; 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=Wl7HEoZMUzGsbQepWMVSfO0JV4YjBapS0e5mq4W7b+4=; b=K1sK9smldBShtXf000EQNmhBNgxOfFC3qZKoYLLo8HhsJd3G+awsitJPeX9IDvgHUyYF4B GBesQuHoBTabYCpl9arlp6y0hSICYq3/jtlgPYgeFZcabooEA9QT4oALjq9In8lnQYRcYI k/8c0OJ2yHh10fay00RXJBytBdk5JK4= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=kA0qCy5s; spf=pass (imf20.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.172 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1767174790; a=rsa-sha256; cv=none; b=heLyEPu0nZ9SQGjhcrG0y7igEGgbMf+JVqJmHusXsx7paXJdRmRLvA41zjxyq0I28NCz6E ONLH3VGahFmSyid9jZ3toaqz3wKD8UFLUQnu2X+pgjPXOOdlM2JRiPpp4APHsIdYXFh0Bs gpCMMtIT1IkBzcUcqH76zC+htKr+ttU= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1767174787; 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=Wl7HEoZMUzGsbQepWMVSfO0JV4YjBapS0e5mq4W7b+4=; b=kA0qCy5swxT9/bUHnpErzkaTUIfgXxao85n1AotjzFLMJUomMkCAQjLXpZ4B+KRO9Tbq2L WU+1OAl5FxBAuCo1I3+CkOeCjPhLEPbag/rozOxh+CRn8kHOwBSKIYK4ige8l1o+gK7jtK Vz5BljGIGicYjbCKFeIBggxM5nn/wOQ= Date: Wed, 31 Dec 2025 17:52:57 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v3 7/7] mm: make PT_RECLAIM depends on MMU_GATHER_RCU_TABLE_FREE To: Wei Yang Cc: will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, dev.jain@arm.com, akpm@linux-foundation.org, david@kernel.org, ioworker0@gmail.com, linmag7@gmail.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-alpha@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, Qi Zheng References: <20251231094243.zmjs7kgflm7q6k73@master> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <20251231094243.zmjs7kgflm7q6k73@master> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: nykufjhkg9ifg9ydfqqzhjgpbdiyeawn X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: D7CE51C0003 X-HE-Tag: 1767174789-456259 X-HE-Meta: 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 PpBKj65b LL/hFMXQzFidxyfQ= 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 12/31/25 5:42 PM, Wei Yang wrote: > On Wed, Dec 17, 2025 at 05:45:48PM +0800, Qi Zheng wrote: >> From: Qi Zheng >> >> The PT_RECLAIM can work on all architectures that support >> MMU_GATHER_RCU_TABLE_FREE, so make PT_RECLAIM depends on >> MMU_GATHER_RCU_TABLE_FREE. >> >> BTW, change PT_RECLAIM to be enabled by default, since nobody should want >> to turn it off. >> >> Signed-off-by: Qi Zheng >> --- >> arch/x86/Kconfig | 1 - >> mm/Kconfig | 9 ++------- >> 2 files changed, 2 insertions(+), 8 deletions(-) >> >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >> index 80527299f859a..0d22da56a71b0 100644 >> --- a/arch/x86/Kconfig >> +++ b/arch/x86/Kconfig >> @@ -331,7 +331,6 @@ config X86 >> select FUNCTION_ALIGNMENT_4B >> imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI >> select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE >> - select ARCH_SUPPORTS_PT_RECLAIM if X86_64 >> select ARCH_SUPPORTS_SCHED_SMT if SMP >> select SCHED_SMT if SMP >> select ARCH_SUPPORTS_SCHED_CLUSTER if SMP >> diff --git a/mm/Kconfig b/mm/Kconfig >> index bd0ea5454af82..fc00b429b7129 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -1447,14 +1447,9 @@ config ARCH_HAS_USER_SHADOW_STACK >> The architecture has hardware support for userspace shadow call >> stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss). >> >> -config ARCH_SUPPORTS_PT_RECLAIM >> - def_bool n >> - >> config PT_RECLAIM >> - bool "reclaim empty user page table pages" >> - default y >> - depends on ARCH_SUPPORTS_PT_RECLAIM && MMU && SMP >> - select MMU_GATHER_RCU_TABLE_FREE >> + def_bool y >> + depends on MMU_GATHER_RCU_TABLE_FREE >> help >> Try to reclaim empty user page table pages in paths other than munmap >> and exit_mmap path. > > Hi, Qi > > I am new to PT_RECLAIM, when reading related code I got one question. > > Before this patch, we could have this config combination: > > CONFIG_MMU_GATHER_RCU_TABLE_FREE & !CONFIG_PT_RECLAIM > > This means tlb_remove_table_free() is rcu version while tlb_remove_table_one() > is semi rcu version. > > I am curious could we use rcu version tlb_remove_table_one() for this case? > Use rcu version tlb_remove_table_one() if CONFIG_MMU_GATHER_RCU_TABLE_FREE. Is > there some limitation here? I think there's no problem. The rcu version can also ensure that the fast GUP works well. > > Thanks in advance for your explanation. > >