From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S271940AbTGRWmn (ORCPT ); Fri, 18 Jul 2003 18:42:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S271919AbTGRWjs (ORCPT ); Fri, 18 Jul 2003 18:39:48 -0400 Received: from ppp-217-133-42-200.cust-adsl.tiscali.it ([217.133.42.200]:33729 "EHLO dualathlon.random") by vger.kernel.org with ESMTP id S271923AbTGRWiY (ORCPT ); Fri, 18 Jul 2003 18:38:24 -0400 Date: Sat, 19 Jul 2003 00:53:28 +0200 From: Andrea Arcangeli To: William Lee Irwin III , Christoph Hellwig , linux-kernel@vger.kernel.org Subject: Re: 2.4.22pre6aa1 Message-ID: <20030718225328.GQ3928@dualathlon.random> References: <20030717102857.GA1855@dualathlon.random> <20030718191853.A11052@infradead.org> <20030718222750.GL3928@dualathlon.random> <20030718224824.GP15452@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030718224824.GP15452@holomorphy.com> User-Agent: Mutt/1.4i X-GPG-Key: 1024D/68B9CB43 13D9 8355 295F 4823 7C49 C012 DFA1 686E 68B9 CB43 X-PGP-Key: 1024R/CB4660B9 CC A0 71 81 F4 A0 63 AC C0 4B 81 1D 8C 15 C8 E5 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 18, 2003 at 03:48:24PM -0700, William Lee Irwin III wrote: > On Sat, Jul 19, 2003 at 12:27:50AM +0200, Andrea Arcangeli wrote: > > bigpages= is a documented API that has to be used in production, so I > > can easily add the hugetlbfs API but I guess I've to keep this one > > anyways. I also would need to verify the performance of hugetlbfs before > > suggesting migrating to it, for example I don't want > > preallocation/prefaulting (IIRC hugetlbfs preallocates everything). I > > also like the single huge array of page pointers, that is very hardwired > > but optimal for those workloads. > > Most of the complaints I've gotten are about lack of support for mixed > PSE and non-PSE mappings, not preallocation or performance (generally > its usage doesn't involve creation/destruction cycle performance > requirements, and most of the time they intend to use 100% of the memory). > > It's basically too stupid and operating on too small a data set to > screw up performance-wise apart from creation/destruction, which is not > intended to be performant (and will never be; it blits oversized areas). > > I wouldn't mind hearing of what you believe is missing, so long as it's > within the constraints of what's mergeable. =( I tend to think the creation/destruction will be the most noticeable performance difference in practice. allocating 42G in a single block will take a bit of time ;). I'm not necessairly worse or unacceptable, but it's different. And I feel I've to retain the bigpages= API (as an API not as in implementation) anyways. Furthmore I'm unsure if hugtlbfs is relaxed like the shm-largpeage patch is, I mean, it should be possible to mmap the stuff with 4k granularty too, or stuff could break due that change of API too. Andrea