From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx112.postini.com [74.125.245.112]) by kanga.kvack.org (Postfix) with SMTP id 523166B0071 for ; Mon, 22 Oct 2012 12:42:43 -0400 (EDT) Received: by mail-ia0-f169.google.com with SMTP id h37so2802679iak.14 for ; Mon, 22 Oct 2012 09:42:42 -0700 (PDT) MIME-Version: 1.0 Reply-To: mtk.manpages@gmail.com In-Reply-To: <20121022162929.GN2095@tassilo.jf.intel.com> References: <1350665289-7288-1-git-send-email-andi@firstfloor.org> <20121022132733.GQ16230@one.firstfloor.org> <20121022133534.GR16230@one.firstfloor.org> <20121022153633.GK2095@tassilo.jf.intel.com> <20121022161151.GS16230@one.firstfloor.org> <20121022162929.GN2095@tassilo.jf.intel.com> From: "Michael Kerrisk (man-pages)" Date: Mon, 22 Oct 2012 18:42:22 +0200 Message-ID: Subject: Re: [PATCH] MM: Support more pagesizes for MAP_HUGETLB/SHM_HUGETLB v6 Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Andi Kleen Cc: Andi Kleen , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hillf Danton On Mon, Oct 22, 2012 at 6:29 PM, Andi Kleen wrote: >> Since PowerPC already allows 16GB page sizes, doesn't there need to be >> allowance for the possibility of future expansion? Choosing a larger >> minimum size (like 2^16) would allow that. Does the minimum size need >> to be 16k? (Surely, if you want a HUGEPAGE, you want a bigger page >> than that? I am not sure.) > > Some architectures have configurable huge page sizes, so it depends on > the user. I thought 16K is reasonable. Can make it larger too. > > But I personally consider even 16GB pages somewhat too big. I do not know the answer course ;-). Just thought that it was worth emphasizing that some system already allows the upper limit you propose. It seems inevitable that some other system will allow something even bigger. Anyway, I got distracted from my earlier more important point. This proposed change will chew up most (all?) of the remaining bit-space in 'flags'. This seems like a mistake from a future extensibility point of view... It sounds a lot like you'll force someone else to write and deploy mmap3()... -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- 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