From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp105.biz.mail.re2.yahoo.com (smtp105.biz.mail.re2.yahoo.com [206.190.52.174]) by ozlabs.org (Postfix) with SMTP id 912E5DDDE7 for ; Sun, 11 Feb 2007 05:04:05 +1100 (EST) In-Reply-To: <1171075021.20494.0.camel@localhost.localdomain> References: <989B956029373F45A0B8AF02970818900D444B@zch01exm26.fsl.freescale.net> <45CB28A6.3050607@freescale.com> <712E63F6-23D6-45EB-92F0-95656FF38BC4@embeddedalley.com> <1171075021.20494.0.camel@localhost.localdomain> Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <6CDAEEF1-B0ED-42E6-AA2C-6FD1CFCF462C@embeddedalley.com> From: Dan Malek Subject: Re: Discussion about iopa() Date: Sat, 10 Feb 2007 13:04:03 -0500 To: Benjamin Herrenschmidt Cc: linuxppc-dev list , Timur Tabi List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Feb 9, 2007, at 9:37 PM, Benjamin Herrenschmidt wrote: > We are fairly careful about not bloating fast path in general. This isn't any fast path code, and the way the exception handlers are growing it doesn't seem to be a concern anyway. > .... It's more > than a couple of memory accesses, especially with PTEs in highmem > where > it involves kmap. It is only a couple of memory accesses, even less code than the TLB exception handlers. Using highmem has a price any time it's configured into a system, it's not unique in this case. In fact, in this case highmem shouldn't be a concern any different than the TLB exceptions. I just don't understand how such a trivial and useful function that does exactly what we need in a very clean way generates so much polarized discussion. I'm beginning to think it's just personal, since the only argument against it is "I don't like it" when the alternatives are just hacks at best that still need to be "fixed up someday." :-) The Linux VM implementation just sucks. The majority of systems running this software aren't servers and desktop PCs, it's embedded SOCs with application specific peripherals. They have attributes and are mapped in ways that don't fit the "memory at 0" or "IO" model. We have to find solutions to this, together. Thanks. -- Dan