From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757912AbZBXOsB (ORCPT ); Tue, 24 Feb 2009 09:48:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755330AbZBXOrx (ORCPT ); Tue, 24 Feb 2009 09:47:53 -0500 Received: from hera.kernel.org ([140.211.167.34]:57672 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754164AbZBXOrw (ORCPT ); Tue, 24 Feb 2009 09:47:52 -0500 Message-ID: <49A4087B.8080405@kernel.org> Date: Tue, 24 Feb 2009 23:47:23 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.19 (X11/20081227) MIME-Version: 1.0 To: Ingo Molnar CC: rusty@rustcorp.com.au, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, jeremy@goop.org, cpw@sgi.com, nickpiggin@yahoo.com.au, ink@jurassic.park.msu.ru Subject: Re: [PATCHSET x86/core/percpu] improve the first percpu chunk allocation References: <1235445101-7882-1-git-send-email-tj@kernel.org> <20090224095708.GA20739@elte.hu> <49A3DE76.5010606@kernel.org> <20090224125132.GB31295@elte.hu> In-Reply-To: <20090224125132.GB31295@elte.hu> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 24 Feb 2009 14:47:27 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Ingo Molnar wrote: --snip-- > So what i'm saying is that these are strong reasons for us to > want to make the unit size to be something like 2MB - on 64-bit > x86 at least. > > ( Using a 2MB unit size will also have another advantage: _iff_ > we can still allocate a hugepage at that point we can map it > straight there when extending the dynamic area. ) Thanks for the explanation. Yeap, it would be nice to have units aligned on 2MB boundary. We'll need to add @align to vm area alloc function to do it correctly. As for using large page, it would be nice if we can do that automatically. Upfront 2MB unit allocation is probably too expensive but merging 4k pages into a large page (if we can get them) will add a lot of irregular latency too. Hmmm... -- tejun