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 2F28EC48BEB for ; Fri, 16 Feb 2024 12:30:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=mMqgu5LUUsvlPAbkvw9bKZ9z3uQnxZMl4riCvHUZ60s=; b=cLEJpZlhq/JXz4 pngFirt34oZ4a3FkVRLxEYuQYlpsXZxuy1Sclsd/xxOoO9IOkhMvmm6rriLes8NlZAFjYncsjMyVO wKtx4TrRNT4AY/m/S3FSrpOPAQXoetC1oqBU8IqGdz9M4rdVCmgE2SxBbRTHNDmZGt05GXRekgh0V or+iM7iysTD6DWLv+GRBdkPLVxTR/pjrEJZjJweXsqqVcONzxH4daewzKs2xNRNffYY+7ftkk6wrd Vr9Y6jWyURHu444GMOwMMoeZ+ARxprB7w0NyH7wqBXOhTsaMAK+kVc9gynkOucIn0I+flH9zaif1Z 9HYWlvaaYk2acbDKpAZg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1raxMH-00000002I1n-0edD; Fri, 16 Feb 2024 12:30:25 +0000 Received: from sin.source.kernel.org ([2604:1380:40e1:4800::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1raxMD-00000002I0m-44lv for linux-arm-kernel@lists.infradead.org; Fri, 16 Feb 2024 12:30:23 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 234B6CE293E; Fri, 16 Feb 2024 12:30:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA0D8C433C7; Fri, 16 Feb 2024 12:30:14 +0000 (UTC) Date: Fri, 16 Feb 2024 12:30:12 +0000 From: Catalin Marinas To: Ryan Roberts Cc: Will Deacon , Ard Biesheuvel , Marc Zyngier , James Morse , Andrey Ryabinin , Andrew Morton , Matthew Wilcox , Mark Rutland , David Hildenbrand , Kefeng Wang , John Hubbard , Zi Yan , Barry Song <21cnbao@gmail.com>, Alistair Popple , Yang Shi , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 13/18] arm64/mm: Implement new wrprotect_ptes() batch API Message-ID: References: <20240215103205.2607016-1-ryan.roberts@arm.com> <20240215103205.2607016-14-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240215103205.2607016-14-ryan.roberts@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240216_043022_193857_159486A0 X-CRM114-Status: GOOD ( 15.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Feb 15, 2024 at 10:32:00AM +0000, Ryan Roberts wrote: > Optimize the contpte implementation to fix some of the fork performance > regression introduced by the initial contpte commit. Subsequent patches > will solve it entirely. > > During fork(), any private memory in the parent must be write-protected. > Previously this was done 1 PTE at a time. But the core-mm supports > batched wrprotect via the new wrprotect_ptes() API. So let's implement > that API and for fully covered contpte mappings, we no longer need to > unfold the contpte. This has 2 benefits: > > - reduced unfolding, reduces the number of tlbis that must be issued. > - The memory remains contpte-mapped ("folded") in the parent, so it > continues to benefit from the more efficient use of the TLB after > the fork. > > The optimization to wrprotect a whole contpte block without unfolding is > possible thanks to the tightening of the Arm ARM in respect to the > definition and behaviour when 'Misprogramming the Contiguous bit'. See > section D21194 at https://developer.arm.com/documentation/102105/ja-07/ > > Tested-by: John Hubbard > Signed-off-by: Ryan Roberts Acked-by: Catalin Marinas _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel