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 4DEC0C48260 for ; Fri, 16 Feb 2024 12:34:23 +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=3+2JVR8PE38SKQyR8jEzySUiizhRSK42ILzWRyaomIg=; b=SSMSxTXrYBpU3F S/9ugJLYMD+s5HqG27P6zz15ayrKqMMbDNytu3UNTR8LFyq9uuhE3mkQb1uFwCakmhWh42tser9j7 LmyLgq0Umkt/klwM/ASRdOuD427dQDzjrmPNunf7e8GMnsZCWKFazzlMaNCX1DedY9DQLkQHDSFbM 9pf9CAEjXrZKJ/k9c0buKxNfhCn80DydiICSi4zJXovwxHsOb1Ox6OAD6mdbhOE5agZ+dlgSKQmNm L+QYlCoE3nvhQt33OqLDeRPiish8HkEUvGF3lQ6uTd2NeCyZRj9RvdUFh2EY9JE/JDF5xm9UmAds6 i8mrSV771yJtubEpJ/2A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1raxPw-00000002Iop-461S; Fri, 16 Feb 2024 12:34:12 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1raxPu-00000002In4-0vAx for linux-arm-kernel@lists.infradead.org; Fri, 16 Feb 2024 12:34:11 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 8DD0C614FA; Fri, 16 Feb 2024 12:34:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4F9B9C433C7; Fri, 16 Feb 2024 12:34:04 +0000 (UTC) Date: Fri, 16 Feb 2024 12:34:02 +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 16/18] arm64/mm: Implement pte_batch_hint() Message-ID: References: <20240215103205.2607016-1-ryan.roberts@arm.com> <20240215103205.2607016-17-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240215103205.2607016-17-ryan.roberts@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240216_043410_326154_54642263 X-CRM114-Status: GOOD ( 14.71 ) 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 10:32:03AM +0000, Ryan Roberts wrote: > When core code iterates over a range of ptes and calls ptep_get() for > each of them, if the range happens to cover contpte mappings, the number > of pte reads becomes amplified by a factor of the number of PTEs in a > contpte block. This is because for each call to ptep_get(), the > implementation must read all of the ptes in the contpte block to which > it belongs to gather the access and dirty bits. > > This causes a hotspot for fork(), as well as operations that unmap > memory such as munmap(), exit and madvise(MADV_DONTNEED). Fortunately we > can fix this by implementing pte_batch_hint() which allows their > iterators to skip getting the contpte tail ptes when gathering the batch > of ptes to operate on. This results in the number of PTE reads returning > to 1 per pte. > > Acked-by: Mark Rutland > Reviewed-by: David Hildenbrand > 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