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 332EBCED617 for ; Tue, 18 Nov 2025 12:03:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 76E726B0089; Tue, 18 Nov 2025 07:03:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 71ECA6B008A; Tue, 18 Nov 2025 07:03:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 634BD6B0093; Tue, 18 Nov 2025 07:03:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 5159D6B0089 for ; Tue, 18 Nov 2025 07:03:45 -0500 (EST) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id E09B55952F for ; Tue, 18 Nov 2025 12:03:44 +0000 (UTC) X-FDA: 84123593568.21.91E04D2 Received: from out-186.mta1.migadu.com (out-186.mta1.migadu.com [95.215.58.186]) by imf06.hostedemail.com (Postfix) with ESMTP id 68E5F180014 for ; Tue, 18 Nov 2025 12:03:41 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Z9Rbcq7i; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf06.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.186 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763467423; 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=YSfDkQJHByC5W64S3r1RZBfV7l+QzHRtZt5IkHkWjXM=; b=j/HOK51pFE/+85blaaocQoXEPdD18g6MQ8FZgM30yBVXEkhA2ih+upHiw1veSgSNmFkXwh 8dH5FpdakbeTpITy2hCirHCvPb1Pi97SfOiUA+hec0qAtsxAcWFgBon+LaFL2CyIYt449P 2afvIY8xWfhgVCLsbWtiTtnPQfoa5bE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763467423; a=rsa-sha256; cv=none; b=bHwmYMctbk4Ze9ZOYF/kdijxXuPV9ANSP3zMOeATUy9Veku/k6tO8i/OgUQD0euayLAIeM 6PnzDtWUrk9o/IkJaOkv+AhlOl7yx45XrIjRsWeHOeU5hS2UUDGofQTKTFCl7BdEAJlm6N qNPUuHoBVZoZeD/mBiuf8b5G1HFYiM4= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Z9Rbcq7i; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf06.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.186 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev Message-ID: <195baf7c-1f4e-46a4-a4aa-e68e7d00c0f9@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1763467417; 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=YSfDkQJHByC5W64S3r1RZBfV7l+QzHRtZt5IkHkWjXM=; b=Z9Rbcq7i2Y1LGHCoUGuTi6ppSLunSulmRKUQ4pjayjy42viyJ+DcXrTYmImrfSRJw+UKR4 UVTRGLFHLTlNdVaXnjT3ixLkagqhNZyq0Aqov/I7FCpMijq/fe4cVtkKv+q+YaHP5txxbN qqqQe//KpgfJbRYA+2BGf/imvJ4aYQ4= Date: Tue, 18 Nov 2025 20:02:30 +0800 MIME-Version: 1.0 Subject: Re: [PATCH 7/7] mm: make PT_RECLAIM depend on MMU_GATHER_RCU_TABLE_FREE && 64BIT To: "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 Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, Qi Zheng References: <0a4d1e6f0bf299cafd1fc624f965bd1ca542cea8.1763117269.git.zhengqi.arch@bytedance.com> <355d3bf3-c6bc-403e-9f19-89259d868611@kernel.org> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <355d3bf3-c6bc-403e-9f19-89259d868611@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 8hppcrzibrrcorxo3o3nh6erf8pn9xx3 X-Rspam-User: X-Rspamd-Queue-Id: 68E5F180014 X-Rspamd-Server: rspam10 X-HE-Tag: 1763467421-75557 X-HE-Meta: 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 sEbev0hL Q/bTfLSRb0P/qP3bCHG6cG0MLOgKombGy8vAAovvdJuvoDrRTWQcxJZzH1zePWRB8KUbGL7Ch0iF8wHv8OUedQIKc4xdaPfOAG6Bcpe/vhOQhroREvgT5kGuKqdzhh4Hy17VxKYWQj1Pey5AF5x4o03Qm1hSC+wuzta3F5VkQUVfqg1r2mb+vYcNo9muNHM1R1k0nUvfKffopYqpfxX2g0RPlMZxfPJE93vxqqhsaug5C+0pEgRC0AQjmJ/EQK189Ar+fif8J9MkRwnyFkrf4fNnRZ9Z70VrbdJQ0yq3XIVtiKZdItYxV7yV8kA== 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 11/18/25 12:57 AM, David Hildenbrand (Red Hat) wrote: > On 14.11.25 12:11, Qi Zheng wrote: >> From: Qi Zheng > > Subject: s/&&/&/ will do. > >> >> Make PT_RECLAIM depend on MMU_GATHER_RCU_TABLE_FREE so that PT_RECLAIM >> can >> be enabled by default on all architectures that support >> MMU_GATHER_RCU_TABLE_FREE. >> >> Considering that a large number of PTE page table pages (such as 100GB+) >> can only be caused on a 64-bit system, let PT_RECLAIM also depend on >> 64BIT. >> >> Signed-off-by: Qi Zheng >> --- >>   arch/x86/Kconfig | 1 - >>   mm/Kconfig       | 6 +----- >>   2 files changed, 1 insertion(+), 6 deletions(-) >> >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >> index eac2e86056902..96bff81fd4787 100644 >> --- a/arch/x86/Kconfig >> +++ b/arch/x86/Kconfig >> @@ -330,7 +330,6 @@ 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 a5a90b169435d..e795fbd69e50c 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -1440,14 +1440,10 @@ 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 >> +    depends on MMU_GATHER_RCU_TABLE_FREE && MMU && SMP && 64BIT > > Who would we have MMU_GATHER_RCU_TABLE_FREE without MMU? (can we drop > the MMU part) OK. > > Why do we care about SMP in the first place? (can we frop SMP) OK. > > But I also wonder why we need "MMU_GATHER_RCU_TABLE_FREE && 64BIT": > > Would it be harmful on 32bit (sure, we might not reclaim as much, but > still there is memory to be reclaimed?)? This is also fine on 32bit, but the benefits are not significant, So I chose to enable it only on 64-bit. I actually tried enabling MMU_GATHER_RCU_TABLE_FREE on all architectures, and apart from sparc32 being a bit troublesome (because it uses mm->page_table_lock for synchronization within __pte_free_tlb()), the modifications were relatively simple. > > If all 64BIT support MMU_GATHER_RCU_TABLE_FREE (as you previously > state), why can't we only check for 64BIT? OK, will do. Thanks, Qi >