From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 3AB906B025E for ; Thu, 5 Jan 2017 06:24:23 -0500 (EST) Received: by mail-pg0-f69.google.com with SMTP id u5so1046903211pgi.7 for ; Thu, 05 Jan 2017 03:24:23 -0800 (PST) Received: from NAM01-SN1-obe.outbound.protection.outlook.com (mail-sn1nam01on0044.outbound.protection.outlook.com. [104.47.32.44]) by mx.google.com with ESMTPS id z30si43650298plh.61.2017.01.05.03.24.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 05 Jan 2017 03:24:22 -0800 (PST) Date: Thu, 5 Jan 2017 12:24:07 +0100 From: Robert Richter Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA Message-ID: <20170105112407.GU4930@rric.localdomain> References: <1481706707-6211-1-git-send-email-ard.biesheuvel@linaro.org> <1481706707-6211-3-git-send-email-ard.biesheuvel@linaro.org> <20170104132831.GD18193@arm.com> <20170104140223.GF18193@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20170104140223.GF18193@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Will Deacon Cc: Ard Biesheuvel , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Catalin Marinas , Andrew Morton , Hanjun Guo , Yisheng Xie , James Morse On 04.01.17 14:02:23, Will Deacon wrote: > Using early_pfn_valid feels like a bodge to me, since having pfn_valid > return false for something that early_pfn_valid says is valid (and is > therefore initialised in the memmap) makes the NOMAP semantics even more > confusing. The concern I have had with HOLES_IN_ZONE is that it enables pfn_valid_within() for arm64. This means that each pfn of a section is checked which is done only once for the section otherwise. With up to 2^18 pages per section we traverse the memblock list by that factor more often. There could be a performance regression. I haven't numbers yet, since the fix causes another kernel crash. And, this is the next problem I have. The crash doesn't happen otherwise. So, either it uncovers another bug or the fix is incomplete. Though the changes look like it should work. This needs more investigation. -Robert -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org