From patchwork Tue Apr 8 09:52:17 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Brodsky X-Patchwork-Id: 14042589 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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9CAA5C369A1 for ; Tue, 8 Apr 2025 09:53:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A38F1280009; Tue, 8 Apr 2025 05:53:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A0E00280001; Tue, 8 Apr 2025 05:53:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8D76F280009; Tue, 8 Apr 2025 05:53:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 718B6280001 for ; Tue, 8 Apr 2025 05:53:45 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id A8676BA168 for ; Tue, 8 Apr 2025 09:53:45 +0000 (UTC) X-FDA: 83310414810.16.6056DFB Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf21.hostedemail.com (Postfix) with ESMTP id 164441C000C for ; Tue, 8 Apr 2025 09:53:43 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf21.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1744106024; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AoW5uPcncPp3axMC3OLXSZhaQ2vhQ+ldUmkYdrG/FME=; b=woF241aK9RyUBqlmRq5XnASnngU4K98O7+EHu8RDAGcmQgMvuqHUi5zuhdNUXreXLpKV61 1Z7HLjtCHRcfzxATU2oREc0q8LT83RgG5HndF+fhldkm72/KLCa4CJ6ehGvTduzfOqFBJL hHhhifB1jD6eziBKHWIhDmQ1KdblDig= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf21.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744106024; a=rsa-sha256; cv=none; b=JZpGPw//+EQuskHJ94WJe02RPrTuV1/Yvg4CXlkhjII2s62uTU/e8tmWCtUXKKy+Kc8BlB x+lTnuaNxg1OyEfmvCRUs2m1sMR922CdaVYdmoLr/Z3VBVNyDz5hp2xN69y3ucxMDqo7R+ I4hI7ZfoThUuVrD1lsyAfMHG8QtLwXA= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3EB2B2328; Tue, 8 Apr 2025 02:53:44 -0700 (PDT) Received: from e123572-lin.arm.com (e123572-lin.cambridge.arm.com [10.1.194.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F29D83F6A8; Tue, 8 Apr 2025 02:53:38 -0700 (PDT) From: Kevin Brodsky To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , Albert Ou , Andreas Larsson , Andrew Morton , Catalin Marinas , Dave Hansen , "David S. Miller" , Geert Uytterhoeven , Linus Walleij , Madhavan Srinivasan , Mark Rutland , Matthew Wilcox , Michael Ellerman , "Mike Rapoport (IBM)" , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Qi Zheng , Ryan Roberts , Will Deacon , Yang Shi , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, x86@kernel.org Subject: [PATCH v2 07/12] mm: Skip ptlock_init() for kernel PMDs Date: Tue, 8 Apr 2025 10:52:17 +0100 Message-ID: <20250408095222.860601-8-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250408095222.860601-1-kevin.brodsky@arm.com> References: <20250408095222.860601-1-kevin.brodsky@arm.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 164441C000C X-Rspamd-Server: rspam05 X-Rspam-User: X-Stat-Signature: mf5wsatq6z65c4d6y61gm6ijhyjokham X-HE-Tag: 1744106023-713978 X-HE-Meta: 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 dFgSnPQw M15MZAhb9Rg2YLxhfbpDTK55HDishW/ZGRXIKKYca6CNpTO2lsc54hKDl7UJlb16ZCymLN5rwHGTLP1EQRF8DZx4xFvlRsQovcoaXX4lY1zlBxSyJvsPECkCAjBkXOQ5tCLUUVqRR+Vrio4/vdcdjD0Fb0DJaPEwfi8szgqquHyaa5wAwj6WhZWzV3MlidritT4URhfHC+gFxO8M= 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: Split page table locks are not used for pgtables associated to init_mm, at any level. pte_alloc_kernel() does not call ptlock_init() as a result. There is however no separate alloc/free functions for kernel PMDs, and pmd_ptlock_init() is called unconditionally. When ALLOC_SPLIT_PTLOCKS is true (e.g. 32-bit architectures or if CONFIG_PREEMPT_RT is selected), this results in unnecessary dynamic memory allocation every time a kernel PMD is allocated. Now that pagetable_pmd_ctor() is passed the associated mm, we can easily remove this overhead by skipping pmd_ptlock_init() if the pgtable is associated to init_mm. No special-casing is needed on the dtor path, as ptlock_free() is already called unconditionally for all levels. (ptlock_free() is a no-op unless a ptlock was allocated for the given PTP.) Signed-off-by: Kevin Brodsky --- include/linux/mm.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 3f48e449574a..ef420f4dc72c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3210,7 +3210,7 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd) static inline bool pagetable_pmd_ctor(struct mm_struct *mm, struct ptdesc *ptdesc) { - if (!pmd_ptlock_init(ptdesc)) + if (mm != &init_mm && !pmd_ptlock_init(ptdesc)) return false; ptdesc_pmd_pts_init(ptdesc); __pagetable_ctor(ptdesc);