Received: by 10.213.65.68 with SMTP id h4csp1560374imn; Mon, 26 Mar 2018 09:54:13 -0700 (PDT) X-Google-Smtp-Source: AG47ELu3YuBk9W/3Lu7bAzvurxDyT7lHbOvxEW+uX3CTpOxMzM06yvLJ3/3OnvRUSlaWNbFDz400 X-Received: by 2002:a17:902:724b:: with SMTP id c11-v6mr26009513pll.192.1522083253607; Mon, 26 Mar 2018 09:54:13 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1522083253; cv=none; d=google.com; s=arc-20160816; b=H2H80j2JrKk7XLIQjaB5ixxHGStoM97ALDBCxHt3rnRqnMMkY5nQhaalaDS8f+ppKF 0aspDtkhbDAb1Oa3p7mJPd1MlonXm+C5z8byT48Vl4vwrIn1L4lR5ZMu+xy8fHEBtsbV zvB/mQF66U2iOwwDR8eyfaXGbAfMJGWuOma8MIdHB8Q7r5L5W3SdifxgvK5y0AkxCpgk uLEmTBiUbJy3JLHqiZjjy7OmMYt6ZuQKEMTGqp5NV6WLjbuFIcYNPDJMtDE1TMZHJ8F0 vRiCSz+f+AV3SQ0zs0nnRBhIbSI0XdHNn30Atg62ijJ4Pd7h388x0nrYijA4Uwp8EPBj zaVA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding:mime-version :references:in-reply-to:message-id:subject:cc:to:from:date :dmarc-filter:arc-authentication-results; bh=3sC+yGXl/SoVBKZYhN9RHfTtkgq1ve6zb46hb/yDS/s=; b=cB4Ur4VdiHloISx4Be5MbDfPB9LeRPqkbtd4oEQfdo0ZkJMyOp1bnna76a1KHs0DVU CmaPQWo5bDY/7BgicSpI+cfPRgFiTge/Bmxg816zy9Py1aHLFFcjcyFwoPzO7xndGG0/ y7ammctPacAruSZmtAQq45SVlYIYwiWBCfZBv/FnfV6+q87WQHTWVZqlVuos1Xfti0S2 JRxm4w9AaB7fAb8BTojQmEi+tKhmtrsAckqNIyyMQK3e+fNERGOkb+tghAcuoblM1+QT pZpBlhcdBvWcNEDzE46jVW+Kd1jTVpaLUkPn864Caz20Hi9AUE+7tn4zVEsdp/T/Udxw mm/w== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id f1si9557977pgs.98.2018.03.26.09.53.58; Mon, 26 Mar 2018 09:54:13 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752370AbeCZQvf (ORCPT + 99 others); Mon, 26 Mar 2018 12:51:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:54982 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751782AbeCZQve (ORCPT ); Mon, 26 Mar 2018 12:51:34 -0400 Received: from gandalf.local.home (cpe-172-100-180-131.stny.res.rr.com [172.100.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3E6F82172B; Mon, 26 Mar 2018 16:51:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E6F82172B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Mon, 26 Mar 2018 12:51:31 -0400 From: Steven Rostedt To: Matthias Schiffer Cc: mingo@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ftrace: fix stddev calculation in function profiler (again) Message-ID: <20180326125131.15fba249@gandalf.local.home> In-Reply-To: References: X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 24 Mar 2018 17:26:38 +0100 Matthias Schiffer wrote: > @@ -905,8 +898,20 @@ static void profile_graph_return(struct ftrace_graph_ret *trace) > > rec = ftrace_find_profiled_func(stat, trace->func); > if (rec) { > + unsigned long long avg, delta1, delta2; > + > rec->time += calltime; > - rec->time_squared += calltime * calltime; > + > + /* Apply Welford's method */ > + delta1 = calltime - rec->avg; > + > + avg = rec->time; > + do_div(avg, rec->counter); Can you find a way not to do a divide in every function call? -- Steve > + rec->avg = avg; > + > + delta2 = calltime - rec->avg; > + > + rec->stddev += delta1 * delta2; > } > > out: