From owner-svn-src-head@freebsd.org Fri Apr 14 15:31:05 2017 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 4EE51D3D91E; Fri, 14 Apr 2017 15:31:05 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 20A07DF3; Fri, 14 Apr 2017 15:31:05 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id v3EFV4H0093448; Fri, 14 Apr 2017 15:31:04 GMT (envelope-from avg@FreeBSD.org) Received: (from avg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id v3EFV4EZ093447; Fri, 14 Apr 2017 15:31:04 GMT (envelope-from avg@FreeBSD.org) Message-Id: <201704141531.v3EFV4EZ093447@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: avg set sender to avg@FreeBSD.org using -f From: Andriy Gapon Date: Fri, 14 Apr 2017 15:31:04 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r316853 - head/cddl/contrib/opensolaris/lib/libdtrace/common 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: 2.1.23 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: Fri, 14 Apr 2017 15:31:05 -0000 Author: avg Date: Fri Apr 14 15:31:04 2017 New Revision: 316853 URL: https://svnweb.freebsd.org/changeset/base/316853 Log: dtrace: fix normalization of stddev aggregation To be upstreamed. Discussed with: Bryan Cantrill MFC after: 2 weeks Sponsored by: Panzura Modified: head/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c Modified: head/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c ============================================================================== --- head/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c Fri Apr 14 15:22:00 2017 (r316852) +++ head/cddl/contrib/opensolaris/lib/libdtrace/common/dt_consume.c Fri Apr 14 15:31:04 2017 (r316853) @@ -389,8 +389,10 @@ dt_stddev(uint64_t *data, uint64_t norma * The standard approximation for standard deviation is * sqrt(average(x**2) - average(x)**2), i.e. the square root * of the average of the squares minus the square of the average. + * When normalizing, we should divide the sum of x**2 by normal**2. */ dt_divide_128(data + 2, normal, avg_of_squares); + dt_divide_128(avg_of_squares, normal, avg_of_squares); dt_divide_128(avg_of_squares, data[0], avg_of_squares); norm_avg = (int64_t)data[1] / (int64_t)normal / (int64_t)data[0];