From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f52.google.com (mail-pa0-f52.google.com [209.85.220.52]) by kanga.kvack.org (Postfix) with ESMTP id 227186B0069 for ; Fri, 17 Oct 2014 18:04:47 -0400 (EDT) Received: by mail-pa0-f52.google.com with SMTP id fb1so1565824pad.39 for ; Fri, 17 Oct 2014 15:04:46 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTP id ov3si2044972pbc.228.2014.10.17.15.04.45 for ; Fri, 17 Oct 2014 15:04:46 -0700 (PDT) Message-ID: <54419265.9000000@intel.com> Date: Fri, 17 Oct 2014 15:04:21 -0700 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH 2/4] mm: introduce new VM_NOZEROPAGE flag References: <1413554990-48512-1-git-send-email-dingel@linux.vnet.ibm.com> <1413554990-48512-3-git-send-email-dingel@linux.vnet.ibm.com> In-Reply-To: <1413554990-48512-3-git-send-email-dingel@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dominik Dingel , Andrew Morton , linux-mm@kvack.org, Mel Gorman , Michal Hocko , Rik van Riel Cc: Andrea Arcangeli , Andy Lutomirski , "Aneesh Kumar K.V" , Bob Liu , Christian Borntraeger , Cornelia Huck , Gleb Natapov , Heiko Carstens , "H. Peter Anvin" , Hugh Dickins , Ingo Molnar , Jianyu Zhan , Johannes Weiner , "Kirill A. Shutemov" , Konstantin Weitz , kvm@vger.kernel.org, linux390@de.ibm.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Martin Schwidefsky , Paolo Bonzini , Peter Zijlstra , Sasha Levin On 10/17/2014 07:09 AM, Dominik Dingel wrote: > diff --git a/include/linux/mm.h b/include/linux/mm.h > index cd33ae2..8f09c91 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -113,7 +113,7 @@ extern unsigned int kobjsize(const void *objp); > #define VM_GROWSDOWN 0x00000100 /* general info on the segment */ > #define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */ > #define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */ > - > +#define VM_NOZEROPAGE 0x00001000 /* forbid new zero page mappings */ > #define VM_LOCKED 0x00002000 > #define VM_IO 0x00004000 /* Memory mapped I/O or similar */ This seems like an awfully obscure use for a very constrained resource (VM_ flags). Is there ever a time where the VMAs under an mm have mixed VM_NOZEROPAGE status? Reading the patches, it _looks_ like it might be an all or nothing thing. Full disclosure: I've got an x86-specific feature I want to steal a flag for. Maybe we should just define another VM_ARCH bit. -- 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