From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e31.co.us.ibm.com (e31.co.us.ibm.com [32.97.110.149]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e31.co.us.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTP id B4A78DDE23 for ; Sat, 5 Jan 2008 07:01:23 +1100 (EST) Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e31.co.us.ibm.com (8.13.8/8.13.8) with ESMTP id m04K11JN013753 for ; Fri, 4 Jan 2008 15:01:01 -0500 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v8.7) with ESMTP id m04K0xPk127006 for ; Fri, 4 Jan 2008 13:01:00 -0700 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m04K0dG1019571 for ; Fri, 4 Jan 2008 13:00:40 -0700 Message-ID: <477E9073.1050900@linux.vnet.ibm.com> Date: Fri, 04 Jan 2008 14:00:51 -0600 From: Jon Tollefson MIME-Version: 1.0 To: Arnd Bergmann Subject: Re: [PATCh v3] powerpc: add hugepagesz boot-time parameter References: <477D68E6.2070108@linux.vnet.ibm.com> <200801040034.25329.arnd@arndb.de> In-Reply-To: <200801040034.25329.arnd@arndb.de> Content-Type: text/plain; charset=ISO-8859-1 Cc: Adam Litke , mel@csn.ul.ie, David Gibson , linuxppc-dev@ozlabs.org, Paul Mackerras , csnook@redhat.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Arnd Bergmann wrote: > We started discussing this in v1, but the discussion got sidetracked: > Is there a technical reason why you don't also allow 1M pages, which > may be useful in certain scenarios? > No, it was mostly a matter of the time I have had and machines easily available to me for testing. I don't know of a technical reason that would prevent supporting 1M huge pages, but would want the tests in the libhugetlbfs suite to pass, etc. > On the Cell/B.E. platforms (IBM/Mercury blades, Toshiba Celleb, PS3), the > second large page size is an option that can be set in a HID SPR > to either 64KB or 1MB. Unfortunately, we can't do these two simultaneously, > but the firmware can change the default and put it into the device tree, > or you could have the kernel override the firmware settings. > > Going a lot further, do you have plans for a fully dynamic hugepage size, > e.g. using a mount option for hugetlbfs? I can see that as rather useful, > but at the same time it's probably much more complicated than the boot time > option. > Eventually we will want to support dynamic huge page sizes. This is already being looked into. In the meantime we can have some flexibility with a boot-time parameter though. > Arnd <>< > Jon