From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762705AbdAEMWz (ORCPT ); Thu, 5 Jan 2017 07:22:55 -0500 Received: from mail-dm3nam03on0070.outbound.protection.outlook.com ([104.47.41.70]:48453 "EHLO NAM03-DM3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1762100AbdAEMWr (ORCPT ); Thu, 5 Jan 2017 07:22:47 -0500 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=Robert.Richter@cavium.com; Date: Thu, 5 Jan 2017 13:22:00 +0100 From: Robert Richter 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 Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA Message-ID: <20170105122200.GV4930@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> <20170105112407.GU4930@rric.localdomain> <20170105120819.GH679@arm.com> MIME-Version: 1.0 Content-Type: text/plain; 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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. > > There could be, but we're trying to fix a bug here. I wouldn't have > thought that walking over pfns like that is done very often. The bug happens on a small number of machines depending on the memory layout. The fix affects all systems. And right know the impact is unclear. > > 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. > > I really can't see how the fix causes a crash, and I couldn't reproduce > it on any of my boards, nor could any of the Linaro folk afaik. Are you > definitely running mainline with just these two patches from Ard? Yes, just both patches applied. Various other solutions were working. -Robert