Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762851AbXEPFck (ORCPT ); Wed, 16 May 2007 01:32:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760617AbXEPFcd (ORCPT ); Wed, 16 May 2007 01:32:33 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:54452 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760330AbXEPFcc (ORCPT ); Wed, 16 May 2007 01:32:32 -0400 Date: Tue, 15 May 2007 22:29:12 -0700 From: Andrew Morton To: Nick Piggin Cc: Christoph Lameter , linux-kernel@vger.kernel.org, Satyam Sharma , Nate Diller Subject: Re: Pagecache zeroing: zero_user_segment, zero_user_segments and zero_user Message-Id: <20070515222912.ae836e00.akpm@linux-foundation.org> In-Reply-To: <464A8DF5.2010903@yahoo.com.au> References: <20070515202442.eeaa49a0.akpm@linux-foundation.org> <464A8DF5.2010903@yahoo.com.au> X-Mailer: Sylpheed 2.4.1 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1325 Lines: 33 On Wed, 16 May 2007 14:52:05 +1000 Nick Piggin wrote: > Christoph Lameter wrote: > > On Tue, 15 May 2007, Andrew Morton wrote: > > > > > >>> The functions above default to KM_USER0 which is also always used when > >>> zero_user_page was called except in one single case. We open code that > >>> single case to draw attention to the spot. > >>> > >> > >>Dunno. fwiw, we decided to _not_ embed KM_USER0 in the callee: we have had > >>some pretty ghastly bugs in the past due to misuse of kmap slots so the > >>idea was to shove the decision into the caller's face, make them think > >>about what they're doing > > > > > > On the other hand non highmem platforms are burdened with always repeating > > the same KM_USER0 in every function call. Isnt it enough to know that > > standard functions use KM_USER0 for their operations? > > Couldn't that be filtered out inline? It is - there is no runtime overhead for non-highmem machines. The problem nowadays is all the developers who don't need, have, compile for or test on highmem machines. - 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/