From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-x231.google.com (mail-wm0-x231.google.com [IPv6:2a00:1450:400c:c09::231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3yWWMK0rs4zDq78 for ; Wed, 8 Nov 2017 01:02:04 +1100 (AEDT) Received: by mail-wm0-x231.google.com with SMTP id p75so3959484wmg.3 for ; Tue, 07 Nov 2017 06:02:04 -0800 (PST) Date: Tue, 7 Nov 2017 17:01:58 +0300 From: "Kirill A. Shutemov" To: "Aneesh Kumar K.V" Cc: Nicholas Piggin , Florian Weimer , "Kirill A. Shutemov" , linuxppc-dev@lists.ozlabs.org, linux-mm , Andrew Morton , Andy Lutomirski , Dave Hansen , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , linux-arch@vger.kernel.org, Ingo Molnar , Linux Kernel Mailing List Subject: Re: POWER: Unexpected fault when writing to brk-allocated memory Message-ID: <20171107140158.iz4b2lchhrt6eobe@node.shutemov.name> References: <24b93038-76f7-33df-d02e-facb0ce61cd2@redhat.com> <20171106192524.12ea3187@roar.ozlabs.ibm.com> <546d4155-5b7c-6dba-b642-29c103e336bc@redhat.com> <20171107160705.059e0c2b@roar.ozlabs.ibm.com> <20171107111543.ep57evfxxbwwlhdh@node.shutemov.name> <20171107222228.0c8a50ff@roar.ozlabs.ibm.com> <20171107122825.posamr2dmzlzvs2p@node.shutemov.name> <20171108002448.6799462e@roar.ozlabs.ibm.com> <2ce0a91c-985c-aad8-abfa-e91bc088bb3e@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <2ce0a91c-985c-aad8-abfa-e91bc088bb3e@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Nov 07, 2017 at 07:15:58PM +0530, Aneesh Kumar K.V wrote: > > > > > If it is decided to keep these kind of heuristics, can we get just a > > small but reasonably precise description of each change to the > > interface and ways for using the new functionality, such that would be > > suitable for the man page? I couldn't fix powerpc because nothing > > matches and even Aneesh and you differ on some details (MAP_FIXED > > behaviour). > > > I would consider MAP_FIXED as my mistake. We never discussed this explicitly > and I kind of assumed it to behave the same way. ie, we search in lower > address space (128TB) if the hint addr is below 128TB. > > IIUC we agree on the below. > > 1) MAP_FIXED allow the addr to be used, even if hint addr is below 128TB but > hint_addr + len is > 128TB. > > 2) For everything else we search in < 128TB space if hint addr is below > 128TB > > 3) We don't switch to large address space if hint_addr + len > 128TB. The > decision to switch to large address space is primarily based on hint addr > > Is there any other rule we need to outline? Or is any of the above not > correct? That's correct. -- Kirill A. Shutemov