From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A85B72C236D; Mon, 17 Nov 2025 16:58:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763398685; cv=none; b=njQeLDahRgbKTkMz8MyKVa3Kbw8XvMa6ZdOyRwu7RU+AVEeY4V8+rSphRuRelrm2kAfRzGMlJ8r9p7IoYZxt3nbI8hwW0wF+/papD0qXphVBYtp58RzMo7OXDQ4SAkr0d4juI72Z7HgN8wY+Z/g8PPA6gWEEDNXVYR+PbavPEbs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763398685; c=relaxed/simple; bh=XI7Dqc8hDG/imiQjwpaa5L5QUXIhiYHcmUsbHNJq770=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qD90mhmYWUD4VPGjw4iwOn/CXcnwonxwmaOmyC8veo1zigU6/KrpfFubJs8clYI08BK7IuHH0SHbmoYO500WM+U/EQuIPR6lNavdOCZ/2ZKIV1tGTtSrrDHlePNmnQBQtvrY2IUJVRf5B2XwpDMzK4p0fB6W+BarMcE3o7PZ5+c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dPT+kdRJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dPT+kdRJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B11DDC116B1; Mon, 17 Nov 2025 16:58:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763398685; bh=XI7Dqc8hDG/imiQjwpaa5L5QUXIhiYHcmUsbHNJq770=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dPT+kdRJmrc++E4JgaDg0HvOn87ub1fN81aujiL3JuYrC+XABLmrn8IKbujtOxjox 06UW28/7RYwaB1AdZehoyv5pTGVprSBAXjHnoKbjSL+FhOIiMfHk/eazN5xF1ef35L iI2y5+BgESdTBJPjDJ0iyZWOBGh7c+XsGh6M04pYgwNZsjWk51POupKSyh33gdm0EP 45y5/jkWLrEhutdIoC4OWF5kMcmkisDNjsD7jjLCsAiCX9ZO+pgaVPoMulUmJlaGb9 4LERACYZwJIsl5lju9+IsQAyONXCgmYbWkB3p/ehSBdOllMUN3kNW2OC6dfYrgwBMJ Dugsm9vMMNdlA== Message-ID: <355d3bf3-c6bc-403e-9f19-89259d868611@kernel.org> Date: Mon, 17 Nov 2025 17:57:58 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 7/7] mm: make PT_RECLAIM depend on MMU_GATHER_RCU_TABLE_FREE && 64BIT To: Qi Zheng , will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, dev.jain@arm.com, akpm@linux-foundation.org, ioworker0@gmail.com Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, Qi Zheng References: <0a4d1e6f0bf299cafd1fc624f965bd1ca542cea8.1763117269.git.zhengqi.arch@bytedance.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <0a4d1e6f0bf299cafd1fc624f965bd1ca542cea8.1763117269.git.zhengqi.arch@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 14.11.25 12:11, Qi Zheng wrote: > From: Qi Zheng Subject: s/&&/&/ > > Make PT_RECLAIM depend on MMU_GATHER_RCU_TABLE_FREE so that PT_RECLAIM can > be enabled by default on all architectures that support > MMU_GATHER_RCU_TABLE_FREE. > > Considering that a large number of PTE page table pages (such as 100GB+) > can only be caused on a 64-bit system, let PT_RECLAIM also depend on > 64BIT. > > Signed-off-by: Qi Zheng > --- > arch/x86/Kconfig | 1 - > mm/Kconfig | 6 +----- > 2 files changed, 1 insertion(+), 6 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index eac2e86056902..96bff81fd4787 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -330,7 +330,6 @@ 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 a5a90b169435d..e795fbd69e50c 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1440,14 +1440,10 @@ 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 > + depends on MMU_GATHER_RCU_TABLE_FREE && MMU && SMP && 64BIT Who would we have MMU_GATHER_RCU_TABLE_FREE without MMU? (can we drop the MMU part) Why do we care about SMP in the first place? (can we frop SMP) But I also wonder why we need "MMU_GATHER_RCU_TABLE_FREE && 64BIT": Would it be harmful on 32bit (sure, we might not reclaim as much, but still there is memory to be reclaimed?)? If all 64BIT support MMU_GATHER_RCU_TABLE_FREE (as you previously state), why can't we only check for 64BIT? -- Cheers David