From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BD582D6CFBA for ; Fri, 23 Jan 2026 04:00:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 041516B0386; Thu, 22 Jan 2026 23:00:10 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 00F7E6B0388; Thu, 22 Jan 2026 23:00:09 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E88806B0389; Thu, 22 Jan 2026 23:00:09 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id D611D6B0386 for ; Thu, 22 Jan 2026 23:00:09 -0500 (EST) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id AA1F3140147 for ; Fri, 23 Jan 2026 03:22:15 +0000 (UTC) X-FDA: 84361780230.04.6B827F6 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) by imf26.hostedemail.com (Postfix) with ESMTP id 2A574140006 for ; Fri, 23 Jan 2026 03:22:11 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=eXPMNHh9; spf=pass (imf26.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.182 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1769138534; h=from:from:sender: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:dkim-signature; bh=DpeJcCHVDm9aGgZT7fLJbUNNelWHXP+Bu4gd7TvaW7g=; b=gXwMaIKWqA7ENETGxzB+skkk595qwO6VLILEfLqxGX9gMMrnFyUlTirSQVm17ZUZpfXS36 lNTpXRhqUoDk5r/pAM5jELhN7Otzqe+pONmlEXQOnI7ZFQeNCUp5f6CXuffb8p91gCq59z 4lGpv7NP+iv2fPNQ060AeN2oCPS5KeA= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=eXPMNHh9; spf=pass (imf26.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.182 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1769138534; a=rsa-sha256; cv=none; b=7H4VnakPI3p3JXHzMb/pQIat/yNffnK5aJ93V3Cu4KJqh3AwCZonW5pfqFoqI8D4APqC9J ayKqExH6Km64B1VwMsDQVoCa4PnIHQE+UO/Lf7f/CqQr7CF9ONCqWigbScoHH6tBLc5chR 5TJq/J1cd/b5vDcMuvNWZ6b8LVsn1fE= 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 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 X-Rspamd-Server: rspam11 X-Stat-Signature: 7cqzdwbzgac4srexhfkwe1nhuu543keb X-Rspam-User: X-Rspamd-Queue-Id: 2A574140006 X-HE-Tag: 1769138531-323942 X-HE-Meta: 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 tm+kFWwJ 90kAjCiLtwxCYM0eOLI8EgAw2kwRp0FS1x1Mq1OfmurMTVk+qlqMfdNOZu4yFI/ilSOxT9cIfibnwwzdup3C5Pj4Z6g7V5IRgBEUvI6LeArwCMsmb8pV4UoXLDyFalRsHUSj2OJXXL53eiZWFaw6dRNm3P1rYne/G/8FiVwCDbVanTLlFzBvWzNJRPKVc2rQucU5yiFRQfUHgekofhosSUoJyc6rsZXhovAuf2otvTxtpwC2SYnDWtVTHsqCnyJ+ZWPcsPx2WpJkqVQswfAK3eAWKLUX/28IQ0hLh2X+sbvWOWL5XeazSduo8pBiPsnbBbfX5r46g7c6RJmcWDLgX6a3Ltn1dKfYGn2Jg 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 1/22/26 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 >