From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932746AbWLSKEv (ORCPT ); Tue, 19 Dec 2006 05:04:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932721AbWLSKEv (ORCPT ); Tue, 19 Dec 2006 05:04:51 -0500 Received: from 1-1-8-31a.gmt.gbg.bostream.se ([82.182.75.118]:61832 "EHLO lin5.shipmail.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932749AbWLSKEu (ORCPT ); Tue, 19 Dec 2006 05:04:50 -0500 X-Greylist: delayed 1216 seconds by postgrey-1.27 at vger.kernel.org; Tue, 19 Dec 2006 05:04:49 EST Message-ID: <4587B47F.20008@tungstengraphics.com> Date: Tue, 19 Dec 2006 10:44:31 +0100 From: =?UTF-8?B?VGhvbWFzIEhlbGxzdHLDtm0=?= User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.7.8) Gecko/20050511 X-Accept-Language: sv, en-us, en MIME-Version: 1.0 To: Arjan van de Ven CC: Dave Jones , Dave Airlie , Linux Kernel list Subject: Re: [patch 1/2] agpgart - allow user-populated memory types. References: <4579ADE3.6040609@tungstengraphics.com> <1165616236.27217.108.camel@laptopd505.fenrus.org> <1095.213.114.71.166.1165619148.squirrel@www.shipmail.org> <1166518064.3365.1188.camel@laptopd505.fenrus.org> In-Reply-To: <1166518064.3365.1188.camel@laptopd505.fenrus.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Arjan van de Ven wrote: >On Sat, 2006-12-09 at 00:05 +0100, Thomas Hellström wrote: > > >>>On Fri, 2006-12-08 at 19:24 +0100, Thomas Hellström wrote: >>> >>> >>>>+ } >>>>+ >>>>+ if (alloc_size <= PAGE_SIZE) { >>>>+ new->memory = kmalloc(alloc_size, GFP_KERNEL); >>>>+ } >>>>+ if (new->memory == NULL) { >>>>+ new->memory = vmalloc(alloc_size); >>>> >>>> >>>this bit is more or less evil as well... >>> >>>1) vmalloc is expensive all the way, higher tlb use etc etc >>>2) mixing allocation types is just a recipe for disaster >>>3) if this isn't a frequent operation, kmalloc is fine upto at least 2 >>>pages; I doubt you'll ever want more >>> >>> >>I understand your feelings about this, and as you probably understand, the >>kfree / vfree thingy is a result of the above allocation scheme. >> >> > >the kfree/vfree thing at MINIMUM should be changed though. Even if you >need both kfree and vfree, you should key it off of a flag that you >store, not off the address of the memory, that's just unportable and >highly fragile. You *know* which allocator you used, so store it and use >THAT info. > > > > > >>The allocated memory holds an array of struct page pointers. The number of >>struct page pointers will range from 1 to about 8192, so the alloc size >>will range from 4bytes to 64K, but could go higher depending on >>architecture. >> >> > >hmm 64Kb is a bit much indeed. You can't do an array of upto 16 entries >with one page in each array entry? > > > Arjan, Thanks for taking time to review this. A short background: The current code uses vmalloc only. The potential use of kmalloc was introduced to save memory and cpu-speed. All agp drivers expect to see a single memory chunk, so I'm not sure we want to have an array of pages. That may require rewriting a lot of code. If it's acceptable I'd like to go for the vmalloc / kmalloc flag, or at worst keep the current vmalloc only but that's such a _huge_ memory waste for small buffers. The flag was the original idea, but unfortunately the agp_memory struct is part of the drm interface, and I wasn't sure we could add a variable to it. DaveJ, is it possible to extend struct agp_memory with a flags field? Regards, Thomas