From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] powerpc: Introduce address space "slices" From: Benjamin Herrenschmidt To: Olof Johansson In-Reply-To: <20070219153315.GA5036@lixom.net> References: <1171867418.18571.3.camel@localhost.localdomain> <20070219153315.GA5036@lixom.net> Content-Type: text/plain Date: Tue, 20 Feb 2007 06:39:23 +1100 Message-Id: <1171913963.18571.33.camel@localhost.localdomain> Mime-Version: 1.0 Cc: linuxppc-dev list , "cbe-oss-dev@ozlabs.org" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2007-02-19 at 09:33 -0600, Olof Johansson wrote: > On Mon, Feb 19, 2007 at 05:43:38PM +1100, Benjamin Herrenschmidt wrote: > > powerpc: Introduce address space "slices" > > > > This patch provide some infrastructure that will allow proper creation > > of special VMAs with different page sizes on powerpc. > > > > The basic issue is to be able to do what hugetlbfs does but with > > different page sizes for some other special filesystems, more > > specifically, my need is: > > > > - hugetlbfs should still work of course :-) > > > > - SPE local store mappings using 64K pages on a 4K base page size > > kernel on Cell > > Why? What is the reason they can't use 4K pages? Reduce TLB/ERAT trashing. SPE MMUs are fairly small, and in setups where an SPE maps all the others, we take a performance hit due to trashing with 4K pages. However, going to full 64K base page size has other drawbacks, especially in setups with little main memory. Ben.