From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 0664A6B0260 for ; Fri, 16 Dec 2016 12:10:34 -0500 (EST) Received: by mail-pg0-f72.google.com with SMTP id b1so6515806pgc.5 for ; Fri, 16 Dec 2016 09:10:33 -0800 (PST) Received: from NAM03-DM3-obe.outbound.protection.outlook.com (mail-dm3nam03on0072.outbound.protection.outlook.com. [104.47.41.72]) by mx.google.com with ESMTPS id w5si8585707pfl.121.2016.12.16.09.10.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 16 Dec 2016 09:10:33 -0800 (PST) Date: Fri, 16 Dec 2016 18:10:16 +0100 From: Robert Richter Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA Message-ID: <20161216170947.GD4930@rric.localdomain> References: <1481706707-6211-1-git-send-email-ard.biesheuvel@linaro.org> <1481706707-6211-3-git-send-email-ard.biesheuvel@linaro.org> <20161215153930.GA8111@rric.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Ard Biesheuvel Cc: "linux-arm-kernel@lists.infradead.org" , Will Deacon , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Catalin Marinas , Andrew Morton , Hanjun Guo , Yisheng Xie , James Morse On 15.12.16 16:07:26, Ard Biesheuvel wrote: > On 15 December 2016 at 15:39, Robert Richter wrote: > > I was going to do some measurements but my kernel crashes now with a > > page fault in efi_rtc_probe(): > > > > [ 21.663393] Unable to handle kernel paging request at virtual address 20251000 > > [ 21.663396] pgd = ffff000009090000 > > [ 21.663401] [20251000] *pgd=0000010ffff90003 > > [ 21.663402] , *pud=0000010ffff90003 > > [ 21.663404] , *pmd=0000000fdc030003 > > [ 21.663405] , *pte=00e8832000250707 > > > > The sparsemem config requires the whole section to be initialized. > > Your patches do not address this. > > > > 96000047 is a third level translation fault, and the PTE address has > RES0 bits set. I don't see how this is related to sparsemem, could you > explain? When initializing the whole section it works. Maybe it uncovers another bug. Did not yet start debugging this. > > > On 14.12.16 09:11:47, Ard Biesheuvel wrote: > >> +config HOLES_IN_ZONE > >> + def_bool y > >> + depends on NUMA > > > > This enables pfn_valid_within() for arm64 and causes the check for > > each page of a section. The arm64 implementation of pfn_valid() is > > already expensive (traversing memblock areas). Now, this is increased > > by a factor of 2^18 for 4k page size (16384 for 64k). We need to > > initialize the whole section to avoid that. > > > > I know that. But if you want something for -stable, we should have > something that is correct first, and only then care about the > performance hit (if there is one) I would prefer to check for a performance penalty *before* we put it into stable. There is nor risk at all with the patch I am proposing. See: https://lkml.org/lkml/2016/12/16/412 -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