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 BAB31279DCD; Mon, 19 Jan 2026 10:18:59 +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=1768817939; cv=none; b=n3U/9BzBFe7BIbWypYWebK5iipgawcA/gsNSNCWlxJP8h0O1md7vGn8JYO2f4ZRaGQnI3hLbMHh38YFFMf13ray14q6nJz0vs/+TuIi0UtuNsuDnrWVJv2JimBUH6jwEhEj8FH9KobkA2YJ0eL6dxmmcoxwVDnFUlbs2hFJ2ov4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768817939; c=relaxed/simple; bh=fChsW6zHlCrxmXpBWFm7rxfPs3w59SiQtBb4E9KHfFg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=WHcCV72g7uzSptMk0zPuyaI3N3saSKaX8pEyt9mcg5/x6zy1yPFy1NfmMTU/a4lbmt19er7T+Cn3AnfuSIwNczwOC6UtSDHLBGKAKo9EKWP/kS9+l5+H3qf3dW4nbGtClfDbAGB4QbZ36OeBiIEX0s8oTRQNR9tAkni5glaE0Go= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=d7bFMmLq; 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="d7bFMmLq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34AFFC2BCB2; Mon, 19 Jan 2026 10:18:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768817939; bh=fChsW6zHlCrxmXpBWFm7rxfPs3w59SiQtBb4E9KHfFg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=d7bFMmLq1M9B8AoeKJQ9vihTU2U179+WmU91kWylvHMAex0kvNr1DQu7ArTzlhgmn 4pPAxBoFN99lPf4XxyZ7tKbta1qikb7XJrp4yQh6co8oYvuotYRIA1NvXdzUJZRifS FxhutMYG4Y4QWgPa5uqAQinVsFZ/C3a1U/Ly553bgwajDO3Eafz7qBAx+ZsgAtcKkO zZN7xdRM9KwgEZWJ72QmBNlK7I+iUWDUAFicFdjUCQSAPYwBG/CXF+M+t1L9sAxu1e JiR+7Xwrb5/DZiknvTj7tiHrF90zeuEV3qr6RB81V4uGa/vwe/R5dc7JkZ36tQyv3/ F3k5MADrrYaOg== Message-ID: Date: Mon, 19 Jan 2026 11:18:52 +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 v3 7/7] mm: make PT_RECLAIM depends on MMU_GATHER_RCU_TABLE_FREE To: Wei Yang , Qi Zheng Cc: will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, dev.jain@arm.com, akpm@linux-foundation.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> <20260101020715.45wqnjgcklvjcth3@master> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/1/26 03:07, Wei Yang wrote: > On Wed, Dec 31, 2025 at 05:52:57PM +0800, Qi Zheng wrote: >> >> >> 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 for your quick response :-) > > And Happy New Year > > So my little suggestion is move the definition of __tlb_remove_table_one() > under CONFIG_MMU_GATHER_RCU_TABLE_FREE. Do you thinks this would be more > clear? Do you mean diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c index 2faa23d7f8d42..6aeba4bae68d2 100644 --- a/mm/mmu_gather.c +++ b/mm/mmu_gather.c @@ -319,7 +319,7 @@ static inline void tlb_table_invalidate(struct mmu_gather *tlb) } } -#ifdef CONFIG_PT_RECLAIM +#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE static inline void __tlb_remove_table_one_rcu(struct rcu_head *head) { struct ptdesc *ptdesc; ? -- Cheers David