From owner-svn-src-head@FreeBSD.ORG Sun Nov 10 13:37:44 2013 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id EB564EB7; Sun, 10 Nov 2013 13:37:44 +0000 (UTC) (envelope-from mav@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:1900:2254:2068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id D7FAF2B2C; Sun, 10 Nov 2013 13:37:44 +0000 (UTC) Received: from svn.freebsd.org ([127.0.1.70]) by svn.freebsd.org (8.14.7/8.14.7) with ESMTP id rAADbiMq083103; Sun, 10 Nov 2013 13:37:44 GMT (envelope-from mav@svn.freebsd.org) Received: (from mav@localhost) by svn.freebsd.org (8.14.7/8.14.5/Submit) id rAADbi6A083102; Sun, 10 Nov 2013 13:37:44 GMT (envelope-from mav@svn.freebsd.org) Message-Id: <201311101337.rAADbi6A083102@svn.freebsd.org> From: Alexander Motin Date: Sun, 10 Nov 2013 13:37:44 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r257916 - head/sys/dev/isp X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 10 Nov 2013 13:37:45 -0000 Author: mav Date: Sun Nov 10 13:37:44 2013 New Revision: 257916 URL: http://svnweb.freebsd.org/changeset/base/257916 Log: Save one more register read per command by not reading rqstoutrp register every time. The purpose of that register is unlikely output queue overflow detection, so read it only when its last known (and probably stale now) value signals overflow. This reduces CPU load and lock congestion and rises bottleneck in CTL while doing target mode via two 8Gbps ports from 100K to 120K IOPS. Modified: head/sys/dev/isp/isp_library.c Modified: head/sys/dev/isp/isp_library.c ============================================================================== --- head/sys/dev/isp/isp_library.c Sun Nov 10 13:16:28 2013 (r257915) +++ head/sys/dev/isp/isp_library.c Sun Nov 10 13:37:44 2013 (r257916) @@ -322,9 +322,13 @@ isp_destroy_handle(ispsoftc_t *isp, uint void * isp_getrqentry(ispsoftc_t *isp) { - isp->isp_reqodx = ISP_READ(isp, isp->isp_rqstoutrp); - if (ISP_NXT_QENTRY(isp->isp_reqidx, RQUEST_QUEUE_LEN(isp)) == isp->isp_reqodx) { - return (NULL); + uint32_t next; + + next = ISP_NXT_QENTRY(isp->isp_reqidx, RQUEST_QUEUE_LEN(isp)); + if (next == isp->isp_reqodx) { + isp->isp_reqodx = ISP_READ(isp, isp->isp_rqstoutrp); + if (next == isp->isp_reqodx) + return (NULL); } return (ISP_QUEUE_ENTRY(isp->isp_rquest, isp->isp_reqidx)); }