From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f47.google.com (mail-ej1-f47.google.com [209.85.218.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 819E52B9B9 for ; Sat, 24 Jan 2026 01:45:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769219158; cv=none; b=ATyOyw1uLbEadiPZE1aMRJjSQ3jwieGXj7KGupqCJOZQ0snXOOAfCCKI64liPZK7gTK6u39xIDerlAsPHwMPaEktEPkMzBuaxc4wdEj6u1cX8zzZhFrN1N6S0dz/j592GUvefCmPLQOkoMZmuw883SFm12S6qLF+7T04mJB8sD0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769219158; c=relaxed/simple; bh=9QeaE1bwD3GxKwFMm007vrZkopgiIxQPdZ7Ly6RtqsU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PsGwa3/9WjxZn6C9owTUUGGAuvzeYy8Bho6ry+w+PkiqjispXbxjnr7e/cw48MuQN/mwQBjzb1QrQLsbTEG20RR16sOFWlyGVnuOYwZhLuHwinkgZumhrQMsvjjkyaxeVMElV1bYnddZVuqiR1hmDp9NeK4B+1kffNvU0vj5yaw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=WsnJhR+M; arc=none smtp.client-ip=209.85.218.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WsnJhR+M" Received: by mail-ej1-f47.google.com with SMTP id a640c23a62f3a-b8715a4d9fdso344353366b.0 for ; Fri, 23 Jan 2026 17:45:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1769219154; x=1769823954; darn=vger.kernel.org; h=user-agent:in-reply-to:content-disposition:mime-version:references :reply-to:message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=ZXp0QJyrLLUrmQyXAB/60kXaLRgyX8FN8f699HysLTo=; b=WsnJhR+Mi1FQ11mGYA7oMNG+Q18NQF6o4cPFnGITlPkbgKlTg4GYPQqnxtKCCvtkrR KRli7UQ2GfZzxCx9E8rwrTndeSyExqFGw7qifPqptU7Svs1rCHtTXRTDrGPAlcsIrzWQ j1L6APPS5+ieA738poh4OnPvDMlE2RwIzmjF0k9gMtKWLVMaWhPgkhJwlRxPPRZp7iki ZJraeYezYLtb1oY5Cby9kKVAlsrnB1lSXoh3LIhM7eQJEUc1OzkeS3HlE1xD+htLfUzn IRAj5cQFEx4eoun1TRg8oM/VIt0mcqGBoeO4nY/HcdDEjB2dMBPbN9oLYgJCrqPqI/aw 75VA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769219154; x=1769823954; h=user-agent:in-reply-to:content-disposition:mime-version:references :reply-to:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=ZXp0QJyrLLUrmQyXAB/60kXaLRgyX8FN8f699HysLTo=; b=wmJjnXcnROoZqwjHb8deAbwIrN7fLxCDOimHrJ1fx1aNHahIDnYMhiTIFW9ogClEfZ uQ6EwOe2t5E3HNy5jfMXE06GxwAsgl8dbmp4oV35taozf8MDTEI2c6xEutPs6e0WJbbh xbEJBIu6lsqdR4jO6c3yxVGAFOqrfq75/w37IK8hXCbYw4e3ZYGbKqS0T67smzknUWOg jDuLtxJg0zKabBzbGbBQde7pWEHrvut3Oec+/Vb0nwv14QMd/kk5hPt8tUxrezbOD/tF fXP+l09lfUAj8xxI4chSDmPzHxcvOQzorhmgP/Rdiv0goVltvlrFD8V1sjDgQtETXN2K MwtA== X-Forwarded-Encrypted: i=1; AJvYcCW85VfYKqJj7kpB9rKLqnSCn6G+fqpr+jDgAy7Qqfxt7zrAh0iDLrVtf21sOzCiVI1QLHMF5dcsg+/XYw==@vger.kernel.org X-Gm-Message-State: AOJu0YwfaIXXv1yDjFK5Jfi5nKfJg8o0TZ8LW/L3TOSYq1o5EJMYKW6l DgCTGnEf+1Nn/hdj+iQbzsnMsML7N4XcpBfA8khYCQopi/b+4zqiJKKb X-Gm-Gg: AZuq6aKLDHxpLN+kBWtqhs/FC4gei1INalVp1seDV25SJTICLPPfoau1fxnY0xQ+NYN aJlS1F9YeNmcFIRDUdFmCOpICjiD8Z669Nxu13ScSVppn7Jglo+/KHoPpryztxwAEpY4ptLf3+W HmHmW+kxZL8oKvDLs15oqUmdgdq6wFJ+drw3Jz9y0neNf4twEDT5LGoEiLCpwHhFToBDvhHrGDp zaOm5XYAWwX0aw8s1AuUHce4PmLZc4ng9Ae6GBirjZWZdpovTBWB7kHK4k7UgcdDrDNc2HPuyEp Nvv7idWGdDp2exdUWK/HyFr+lYEGzVOStv2nJ9ONczdCZo7vNJ/0uUj37/cVVYeeaGhtfuSbTZ/ kmNEwglbRPNfUDRNIZ891RL+FBWw01tCKN2IlpCgBbxE6yftra2NaMhw2v/vlB4MlsU1Z1j+E0/ yQXR6Q1bN5Hw== X-Received: by 2002:a17:907:3f03:b0:b7a:18ba:a63 with SMTP id a640c23a62f3a-b885ac2bd1dmr330014466b.19.1769219153636; Fri, 23 Jan 2026 17:45:53 -0800 (PST) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b886a249e69sm125246466b.6.2026.01.23.17.45.52 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Fri, 23 Jan 2026 17:45:52 -0800 (PST) Date: Sat, 24 Jan 2026 01:45:52 +0000 From: Wei Yang To: Qi Zheng Cc: Wei Yang , "David Hildenbrand (Red Hat)" , 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 Subject: Re: [PATCH v3 7/7] mm: make PT_RECLAIM depends on MMU_GATHER_RCU_TABLE_FREE Message-ID: <20260124014552.um257bwrhwjktdca@master> Reply-To: Wei Yang References: <20251231094243.zmjs7kgflm7q6k73@master> <20260101020715.45wqnjgcklvjcth3@master> <20260122140034.ymigrfppzwvmcjkr@master> Precedence: bulk X-Mailing-List: linux-alpha@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) On Fri, Jan 23, 2026 at 11:21:50AM +0800, Qi Zheng wrote: > > >On 1/22/26 10:00 PM, Wei Yang wrote: >> On Mon, Jan 19, 2026 at 11:18:52AM +0100, David Hildenbrand (Red Hat) wrote: >> > 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; >> > >> > ? >> >> Sorry for the late reply. >> >> Yes, and maybe we can move the definition to the >> #ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE code block above, then to be next to >> tlb_remove_table_free(). >> >> So that we always have rcu version when CONFIG_MMU_GATHER_RCU_TABLE_FREE. > >LGTM, could you help submit an official patch? > Sure. Since this is trivial cleanup, I will post it till next merge window. >Thanks, >Qi > >> >> > >> > -- >> > Cheers >> > >> > David >> -- Wei Yang Help you, Help me