Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759145AbZFIJjc (ORCPT ); Tue, 9 Jun 2009 05:39:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755557AbZFIJjY (ORCPT ); Tue, 9 Jun 2009 05:39:24 -0400 Received: from cantor.suse.de ([195.135.220.2]:53887 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754571AbZFIJjX (ORCPT ); Tue, 9 Jun 2009 05:39:23 -0400 Date: Tue, 9 Jun 2009 11:39:18 +0200 From: Nick Piggin To: Linus Torvalds Cc: Rusty Russell , Ingo Molnar , Jeremy Fitzhardinge , "H. Peter Anvin" , Thomas Gleixner , Linux Kernel Mailing List , Andrew Morton , Peter Zijlstra , Avi Kivity , Arjan van de Ven Subject: Re: [benchmark] 1% performance overhead of paravirt_ops on native kernels Message-ID: <20090609093918.GC16940@wotan.suse.de> References: <4A0B62F7.5030802@goop.org> <200906032208.28061.rusty@rustcorp.com.au> <200906041554.37102.rusty@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1603 Lines: 37 On Thu, Jun 04, 2009 at 08:02:14AM -0700, Linus Torvalds wrote: > > > On Thu, 4 Jun 2009, Rusty Russell wrote: > > > > > > Turn off HIGHMEM64G, please (and HIGHMEM4G too, for that matter - you > > > can't compare it to a no-highmem case). > > > > Thanks, your point is demonstrated below. I don't think HIGHMEM4G is > > unreasonable for a distro tho, so I turned that on instead. > > Well, I agree that HIGHMEM4G is a _reasonable_ thing to turn on. > > The thing I disagree with is that it's at all valid to then compare to > some all-software feature thing. HIGHMEM doesn't expand any esoteric > capability that some people might use - it's about regular RAM for regular > users. > > And don't get me wrong - I don't like HIGHMEM. I detest the damn thing. I > hated having to merge it, and I still hate it. It's a stupid, ugly, and > very invasive config option. It's just that it's there to support a > stupid, ugly and very annoying fundamental hardware problem. I was looking forward to be able to get rid of it... unfortunately other 32-bit architectures are starting to use it again :( I guess it is not incredibly intrusive for generic mm code. A bit of kmap sprinkled around which is actually quite a useful delimiter of where pagecache is addressed via its kernel mapping. Do you hate more the x86 code? Maybe that can be removed? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/