From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 28 Jun 2003 20:07:06 -0700 From: "Martin J. Bligh" Subject: Re: 2.5.73-mm2 Message-ID: <4160000.1056856024@[10.10.2.4]> In-Reply-To: <20030629021809.GA26348@holomorphy.com> References: <20030627202130.066c183b.akpm@digeo.com> <20030628155436.GY20413@holomorphy.com> <20030628170837.A10514@infradead.org> <56960000.1056846845@[10.10.2.4]> <20030629021809.GA26348@holomorphy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: William Lee Irwin III Cc: Christoph Hellwig , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: --William Lee Irwin III wrote (on Saturday, June 28, 2003 19:18:09 -0700): > On Sat, Jun 28, 2003 at 05:34:05PM -0700, Martin J. Bligh wrote: >> Last time I measured it, it had about a 10% overhead in kernel time. >> Seems like a good thing to keep as an option to me. Bill said he >> had some other code to alleviate the overhead, but I don't think >> it's merged ... I'd rather see UKVA (permanently map the pagetables >> on a per-process basis) merged before it becomes "not an option" - >> that gets rid of all the kmapping. > > There are several orthogonal things going on here. One is dropping the > hooks in the right places to get various concrete tasks done. Another > is general resource scalability vs. raw overhead tradeoffs. The last > one is gathering a wide enough repertoire of core hooks that arches can > use "advanced" techniques like recursive pagetables when they require > various kinds of intervention by the kernel to use. > > This is just another set of hooks we'll need for our end goal, with a > fully functional implementation. It has direct applications and is > completely usable now for resource scalability albeit with some > overhead. Things are all headed in the appropriate directions; the > hooks do not conflict with and do not require any core modifications > whatsoever in order to use in combination with recursive pagetables; > they can simply recover information from already-available places and > transparently replace the highpmd and highpte arch code. > > I can work directly with Dave to arrange a proper demonstration of this > (i.e. fully functional implementation) if need be. I've largely avoided > interceding in recursive pagetable mechanics in order not to duplicate > work. Right, I'm not against what you're doing - I'm totally for it. My only concern was that whilst it has some overhead, it should stay as a config option (which you did). That lets people make the call of overhead vs resource scaling. Your patch is fine - just the talk of removing the config option scared me ;-) M. -- 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: aart@kvack.org