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 058AEC04FF0 for ; Thu, 11 Apr 2024 15:25:59 +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=Gm9paYPoRq3DN9io5wPlAIkDboIUJbq/XEboeZ4GbBE=; b=jMCdQzN34VUler p+m2LG3czg3yBqfwKu+zSy+iA74VSfYKpUa6VMzNngSjVTL1I5kBh9PxAxE32bxHr7yRGfCO0bvXn H8P7X371PAj5d0EB19Ie0G6pqcBzFUVgH1SajKB7kjVDvE/UA9HKxdVNOMcfS/nUIrrQgKPeLtcNi Ufh9hVJJ0srvSnKggkWyyJtOswWRSwMM0w99wH+6bZh7Ax3a4t4g4NhJbJLAXGq/s7iZCh5GjrLww RWRua4tcWNhXmGu05iWDg8uAD1d5Zj2DrsfWIns5tzcywwobPNgGh+QBlvMmfGpqbOuKWY/q2nhEt Tt/sXgrwPuQiL5l1f1Wg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1ruwJ9-0000000Cj5B-1mha; Thu, 11 Apr 2024 15:25:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1ruwJ6-0000000Cj3D-2S35 for linux-arm-kernel@lists.infradead.org; Thu, 11 Apr 2024 15:25:45 +0000 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 2198A113E; Thu, 11 Apr 2024 08:26:12 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.16.129]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C7F7E3F6C4; Thu, 11 Apr 2024 08:25:40 -0700 (PDT) Date: Thu, 11 Apr 2024 16:25:37 +0100 From: Mark Rutland To: Ryan Roberts Cc: Catalin Marinas , Will Deacon , Ard Biesheuvel , David Hildenbrand , Donald Dutile , Eric Chanudet , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Itaru Kitayama Subject: Re: [PATCH v2 3/4] arm64: mm: Don't remap pgtables for allocate vs populate Message-ID: References: <20240404143308.2224141-1-ryan.roberts@arm.com> <20240404143308.2224141-4-ryan.roberts@arm.com> <37d4c278-3780-49ce-bd7e-e8f2ff4501fd@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240411_082544_715892_7C343E01 X-CRM114-Status: GOOD ( 17.13 ) 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, Apr 11, 2024 at 03:57:04PM +0100, Ryan Roberts wrote: > On 11/04/2024 15:48, Mark Rutland wrote: > > On Thu, Apr 11, 2024 at 02:37:49PM +0100, Ryan Roberts wrote: > >> On 11/04/2024 14:02, Mark Rutland wrote: > >>> but the logic remains fairly simple, and I suspect the overhead for late > >>> allocations might not matter since the bulk of late changes are non-allocating. > >> > >> Its just the fixmap overhead that remains... > > > > True; my thinking there is that almost all of the later changes are for smaller > > ranges than the linear map (~10s of MB vs GBs in your test data), so I'd expect > > the overhead of those to be dominated by the cost of mappin the linear map. > > > > The only big exception is arch_add_memory(), but memory hotplug is incredibly > > rare, and we're not making it massively slower than it already was... > > What about something like coco guest mem (or whatever its called). Isn't that > scrubbed out of the linear map? So if a coco VM is started with GBs of memory, > could that be a real case we want to optimize? I think that's already handled -- the functions we have to carve portions out of the linear map use apply_to_page_range(), which doesn't use the fixmap. See set_memory_*() and set_direct_map_*() in arch/arm64/mm/pageattr.c. Note that apply_to_page_range() does what its name implies and *only* handles mappings at page granularity. Hence not using that for mark_linear_text_alias_ro() and mark_rodata_ro() which need to be able to handle blocks. Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel