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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 02D1CEE57F7 for ; Wed, 31 Dec 2025 09:53:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Wl7HEoZMUzGsbQepWMVSfO0JV4YjBapS0e5mq4W7b+4=; b=saWq+zsaJiZpucvrr13o66hl+j iiHIWokkiBt1M6Li+A2lYpKP4utyp+5GQ5EzwapGeYF1BNp8+hWh6yUC/ydGVcA4uP42Ez7HjvQC2 8m3Kjw9Sl7GZPO0jz3Uj29NNwFBIlCnlixjlOhCX36160i0qZIsbkkpi5ldYzT33p1Gf+KgHtWlS2 BRox9czrmAhBZseAj0X+ShREQS8h7lSc3nkMsqAsnaooch5NHkRtTAfW2ALkv/JKxt58ZQL1UKUzD 9UBnSqm7pjShO/Pxu6aUIXUUsCfXT1Vy0q5ZYUvMm7iINV+o8JL+Q6889Ap6u+dPunw8gwghbE282 KT4WO8AQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vastJ-00000005qj5-060h; Wed, 31 Dec 2025 09:53:17 +0000 Received: from out-180.mta1.migadu.com ([2001:41d0:203:375::b4]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vastE-00000005qig-2yg5 for linux-um@lists.infradead.org; Wed, 31 Dec 2025 09:53:15 +0000 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 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251231_015313_963454_750A86BE X-CRM114-Status: GOOD ( 19.45 ) X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org 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. > >