Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750937AbVJGIZ2 (ORCPT ); Fri, 7 Oct 2005 04:25:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751096AbVJGIZ2 (ORCPT ); Fri, 7 Oct 2005 04:25:28 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:42380 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1750937AbVJGIZ1 (ORCPT ); Fri, 7 Oct 2005 04:25:27 -0400 Subject: Re: [RFC] add sysfs to dynamically control blk request tag maintenance From: Arjan van de Ven To: Jens Axboe Cc: "Chen, Kenneth W" , linux-kernel@vger.kernel.org In-Reply-To: <20051007080620.GQ2889@suse.de> References: <20051007074138.GP2889@suse.de> <1128671408.2921.12.camel@laptopd505.fenrus.org> <20051007080620.GQ2889@suse.de> Content-Type: text/plain Date: Fri, 07 Oct 2005 10:25:20 +0200 Message-Id: <1128673521.4145.1.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-Spam-Score: 2.9 (++) X-Spam-Report: SpamAssassin version 3.0.4 on pentafluge.infradead.org summary: Content analysis details: (2.9 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.1 RCVD_IN_SORBS_DUL RBL: SORBS: sent directly from dynamic IP address [80.57.133.107 listed in dnsbl.sorbs.net] 2.8 RCVD_IN_DSBL RBL: Received via a relay in list.dsbl.org [] X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 828 Lines: 19 > The request itself has been > touched by scsi_end_request() already, so unless the layout is really > bad we shouldn't need to fetch a lot of cache lines there. That leaves > __test_and_clear_bit(), I guess that must be it. __test_and_clear_bit() is cheap; it's a single non-locked instruction. Arguably it should be converted into a C variant so that the compiler can pick the best code sequence (I'm not so sure the asm we picked for this is optimal for all processors, I bet it'll be microcoded) but I'd be surprised if it'd be more than a handful of cycles no matter what. - 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/