From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f197.google.com (mail-wj0-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id 567286B025E for ; Fri, 2 Dec 2016 09:06:01 -0500 (EST) Received: by mail-wj0-f197.google.com with SMTP id he10so4630527wjc.6 for ; Fri, 02 Dec 2016 06:06:01 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id lt8si5365750wjb.107.2016.12.02.06.06.00 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 02 Dec 2016 06:06:00 -0800 (PST) Date: Fri, 2 Dec 2016 15:05:57 +0100 From: Michal Hocko Subject: Re: [PATCH v2 0/6] mm: fix the "counter.sh" failure for libhugetlbfs Message-ID: <20161202140556.GN6830@dhcp22.suse.cz> References: <1479107259-2011-1-git-send-email-shijie.huang@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1479107259-2011-1-git-send-email-shijie.huang@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Huang Shijie Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, n-horiguchi@ah.jp.nec.com, kirill.shutemov@linux.intel.com, aneesh.kumar@linux.vnet.ibm.com, gerald.schaefer@de.ibm.com, mike.kravetz@oracle.com, linux-mm@kvack.org, will.deacon@arm.com, steve.capper@arm.com, kaly.xin@arm.com, nd@arm.com, linux-arm-kernel@lists.infradead.org On Mon 14-11-16 15:07:33, Huang Shijie wrote: > (1) Background > For the arm64, the hugetlb page size can be 32M (PMD + Contiguous bit). > In the 4K page environment, the max page order is 10 (max_order - 1), > so 32M page is the gigantic page. > > The arm64 MMU supports a Contiguous bit which is a hint that the TTE > is one of a set of contiguous entries which can be cached in a single > TLB entry. Please refer to the arm64v8 mannul : > DDI0487A_f_armv8_arm.pdf (in page D4-1811) > > (2) The bug > After I tested the libhugetlbfs, I found the test case "counter.sh" > will fail with the gigantic page (32M page in arm64 board). > > This patch set adds support for gigantic surplus hugetlb pages, > allowing the counter.sh unit test to pass. Andrew, I have noticed that this patchset is sitting in the mmotm tree already. I have to say I am not really happy about the changes it is introducing. It is making a confused code base even more so. I have already commented on respective patches but in general I think it needs a deeper thought before it can be merged. -- Michal Hocko SUSE Labs -- 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