Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932236AbWBXPEZ (ORCPT ); Fri, 24 Feb 2006 10:04:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932242AbWBXPEZ (ORCPT ); Fri, 24 Feb 2006 10:04:25 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:21986 "HELO iolanthe.rowland.org") by vger.kernel.org with SMTP id S932236AbWBXPEX (ORCPT ); Fri, 24 Feb 2006 10:04:23 -0500 Date: Fri, 24 Feb 2006 10:04:23 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Benjamin LaHaise cc: Andrew Morton , , Kernel development list Subject: Re: [PATCH] Avoid calling down_read and down_write during startup In-Reply-To: <20060224144028.GB7101@kvack.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 950 Lines: 22 On Fri, 24 Feb 2006, Benjamin LaHaise wrote: > On Thu, Feb 23, 2006 at 10:18:18PM -0500, Alan Stern wrote: > > Ben, earlier you expressed concern about the extra overhead due to > > cache-line contention (on SMP) in the down_read() call added to > > blocking_notifier_call_chain. I don't remember which notifier chain in > > particular you were worried about; something to do with networking. > > > > Does this still bother you? I can see a couple of ways around it. > > Yes it's a problem. Any read lock is going to act as a memory barrier, > and we need fewer of those in hot paths, not more to slow things down. What do you think of the two suggestions in my previous message? Alan Stern - 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/