Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751463AbbGMOB0 (ORCPT ); Mon, 13 Jul 2015 10:01:26 -0400 Received: from resqmta-ch2-05v.sys.comcast.net ([69.252.207.37]:52428 "EHLO resqmta-ch2-05v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751031AbbGMOBZ (ORCPT ); Mon, 13 Jul 2015 10:01:25 -0400 Date: Mon, 13 Jul 2015 09:01:23 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@east.gentwo.org To: Peter Zijlstra cc: Chris Mason , Andy Lutomirski , "ksummit-discuss@lists.linuxfoundation.org" , "linux-kernel@vger.kernel.org" , Jens Axboe , Mathieu Desnoyers , Shaohua Li Subject: Re: [Ksummit-discuss] [CORE TOPIC] lightweight per-cpu locks / restartable sequences In-Reply-To: <20150713095757.GW19282@twins.programming.kicks-ass.net> Message-ID: References: <20150709190916.GI1522@ret.masoncoding.com> <20150713095757.GW19282@twins.programming.kicks-ass.net> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1152 Lines: 27 On Mon, 13 Jul 2015, Peter Zijlstra wrote: > Now the 'problem' is finding these special regions fast, the easy > solution is the same as the one proposed for userspace, one big section. > That way the interrupt only has to check if the IP is inside this > section which is minimal effort. > > The down side is that all percpu ops would then end up being full > function calls. Which on some archs is indeed faster than disabling > interrupts, but not by much I'm afraid. Well one could move the entire functions that are using these ops into the special sections. That is certainly an area requiring much more thought. > > optimize the x86 variants if interrupts also can detect critical sections > > and restart at defined points. > > I really don't see how we can beat %GS prefixes with any such scheme. We may be able to avoid RMV sequences which allows the processor to better schedule operations. -- 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/