From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) (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 53AB4315D5F for ; Wed, 31 Dec 2025 09:53:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.183 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767174802; cv=none; b=Mqc7wyAsG0V/yhKmbd4C3rRFuROt1cIm+sBsoRTl16wXSPdbtUNKGgOJfxFQVHmgbul4kbeTMm7RC9AUORtS53LfCDtkAoPTWJauW9Q+VQwRdDH0xfkAluts+sNGXAvtLLQvCsoMk0IBieZacQzi+eIu+5EvT/iAdWiA3bpyijw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767174802; c=relaxed/simple; bh=bgKG/XkgrbCcQBOUfd1V/7rkB3OG4Wmzv5QaKooC00k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mQKqypyBqvwtaQqqZycmhWbRGDihmUc0z5L+wOy+gHE6c2rSMO+6ub5LQF7Yagbf/uhSF6xpyer/3qPW/BklXbz38B7V9a1zPf4xVXbldO4LiBZfSNIExWHiFsPj53sdIq0LIpSTqQYg0zuqejEk5l84Jpq4yhFbv8/UuxdFmok= 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=kA0qCy5s; arc=none smtp.client-ip=95.215.58.183 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="kA0qCy5s" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1767174787; 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=Wl7HEoZMUzGsbQepWMVSfO0JV4YjBapS0e5mq4W7b+4=; b=kA0qCy5swxT9/bUHnpErzkaTUIfgXxao85n1AotjzFLMJUomMkCAQjLXpZ4B+KRO9Tbq2L WU+1OAl5FxBAuCo1I3+CkOeCjPhLEPbag/rozOxh+CRn8kHOwBSKIYK4ige8l1o+gK7jtK Vz5BljGIGicYjbCKFeIBggxM5nn/wOQ= Date: Wed, 31 Dec 2025 17:52:57 +0800 Precedence: bulk X-Mailing-List: linux-arch@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 Cc: will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, dev.jain@arm.com, akpm@linux-foundation.org, david@kernel.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> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <20251231094243.zmjs7kgflm7q6k73@master> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT 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 in advance for your explanation. > >