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imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=d7bFMmLq; spf=pass (imf11.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1768817940; a=rsa-sha256; cv=none; b=vbJrROKgRDYsFQfSO+ueho301zEd3SePttQwpx9C+jfRD7crq6eDeNSOoi3Tz6v/Gn70l+ IYvpkB8nEAGnkts8NlKa8etmpjFaowncEW+iIb1KrFhrFA3qGxG67uig6v6a9zQc6T3ofy e6TM25m5fxOvSdXqHh4WLYTXyFMURAs= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 7C34443303; Mon, 19 Jan 2026 10:18:59 +0000 (UTC) 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 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 X-Rspamd-Queue-Id: BA0DB40008 X-Stat-Signature: 7d39dyebctwcoxfqb7qdud6bc1wsxk3u X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1768817940-877916 X-HE-Meta: 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 1vhAja2c qBbJkSagNCTLkzA+blNz3HTkhhS6jJHygQkSDVnWzGRP03z3zVpbUtIdUsB8YdcGcc7NLvQjFdsCTdhEUxcu+DF8+D9Y92O/vm3g3yLpiIaXrn5LMQlZiPpYi0TnEVN6BD+GrsjGvveRvu1GaevlOOL7Ht0kctbiVbeVEAEOKXdhBTmscEDG39/5/ll+kYs4/f11E5yPWF/EtjI0n8edqy3UuvjbWlkm4NvTp6zRdNu+2oo+2eCgSJJQw+MTiZDTBr7sv7XOCPYKooZkKGTY7jK1eOeiLts5j8ISZfZ+wIYO+6KxIyyEIqgGG8dBroAeUEfxDfG8RT+o/RoeAfL6fLPsTyAuBQe8bY0zH0bGAAQp2c3b8M1yRijwlwSchM+E+U5QZgzho5L2EE1rnJvWiosEEsw== 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 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