From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) (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 9B1D032AABB for ; Fri, 23 Jan 2026 03:22:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769138548; cv=none; b=VrK3AUqN9kwz6cI+Q84M+pn1Poh65uMb1w/pSb9QExFmLlCxnhg84V8wbHAQwcIQSAWqeeYwGAgNmWSaMP6uKnMtU11Qs0ClRxRRbi7PfKTE6fvvOCuGST++lKlZgxyWDPKZxKqn8kIAJ2+XN7haeqX66SCScEtwoo3l/pYnSWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769138548; c=relaxed/simple; bh=2Zps9dtzhRYJ8wFG0/fas+U5uJPmFW1YcxCoA4RkDFw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=m8AU3VK4nchjzD0s2m7piVdd/aUKzF6pL//Obh4RmpwN1MJ+GCVk8o1ExaVi2fQeQrwBBpzt+5rnJD2mNJxWdU+ZnNb5xxGucF3r/pfjfng8qET37HdjCEt7AKAE1gJG8uhpwk+B1nxy4VLGIMILVOs34JHPrLJwNlc5Cev7MNc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=eXPMNHh9; arc=none smtp.client-ip=95.215.58.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="eXPMNHh9" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1769138529; 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=DpeJcCHVDm9aGgZT7fLJbUNNelWHXP+Bu4gd7TvaW7g=; b=eXPMNHh9ctUnhtpd2wXxPJprv0KOzhjIIb/JZN2sRw4sr1qJsj2GswbWUwjQC99xFlGN+J QxtDjJNo/hWzlNu69ifrt1uEPxLsnWQciI1TqcX0DRrEmtCLkDY/tqkEIuT8fAicEwvtwZ cI4zum4BNHwOopAuRPtAWL6yfr/S8g4= Date: Fri, 23 Jan 2026 11:21:50 +0800 Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v3 7/7] mm: make PT_RECLAIM depends on MMU_GATHER_RCU_TABLE_FREE To: Wei Yang , "David Hildenbrand (Red Hat)" 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> <20260122140034.ymigrfppzwvmcjkr@master> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <20260122140034.ymigrfppzwvmcjkr@master> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT 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? Thanks, Qi > >> >> -- >> Cheers >> >> David >