Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993225Ab2KOKXW (ORCPT ); Thu, 15 Nov 2012 05:23:22 -0500 Received: from vaxjo.synopsys.com ([198.182.60.75]:35243 "EHLO vaxjo.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2993178Ab2KOKXT (ORCPT ); Thu, 15 Nov 2012 05:23:19 -0500 Message-ID: <50A4C273.10102@synopsys.com> Date: Thu, 15 Nov 2012 15:52:43 +0530 From: Vineet Gupta User-Agent: Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 To: Arnd Bergmann CC: , , Subject: Re: [RFC Patch v1 32/55] ARC: [optim] Cache "current" in Register r25 References: <1352720953-24321-1-git-send-email-vgupta@synopsys.com> <1352720953-24321-2-git-send-email-vgupta@synopsys.com> <201211121350.12810.arnd@arndb.de> In-Reply-To: <201211121350.12810.arnd@arndb.de> Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.205] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1253 Lines: 31 On Monday 12 November 2012 07:20 PM, Arnd Bergmann wrote: > On Monday 12 November 2012, Vineet.Gupta1@synopsys.com wrote: >> endmenu # "Platform Board Configuration" >> >> +config ARC_CURR_IN_REG >> + bool "Dedicate Register r25 for current_task pointer" >> + default y >> + help >> + This reserved Register R25 to point to Current Task in >> + kernel mode. This saves memory access for each such access >> + > This looks like a useful feature if you have 32 GPRs, but why make it > optional? Are there cases where you would disable it? Since it touched the low level guts of port, it made sense to start with a config option in initial implementation. But I've kept it that way since it annotates the code nicely and implicitly documents how to do this for any other register + data structure. > Another alternative to caching "current" would be to cache the per-cpu > offset, and calculate current from that one. Good tip - I'll add this to my TODO list - > Arnd -- 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/