From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934468AbdDGRuP (ORCPT ); Fri, 7 Apr 2017 13:50:15 -0400 Received: from mga14.intel.com ([192.55.52.115]:9472 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932905AbdDGRuI (ORCPT ); Fri, 7 Apr 2017 13:50:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,166,1488873600"; d="scan'208";a="71157035" Date: Fri, 7 Apr 2017 10:50:06 -0700 From: Andi Kleen To: Peter Zijlstra Cc: Jin Yao , acme@kernel.org, jolsa@kernel.org, mingo@redhat.com, alexander.shishkin@linux.intel.com, Linux-kernel@vger.kernel.org, kan.liang@intel.com, yao.jin@intel.com, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v2 2/5] perf/x86/intel: Record branch type Message-ID: <20170407175006.GB4021@tassilo.jf.intel.com> References: <1491562066-7472-1-git-send-email-yao.jin@linux.intel.com> <1491562066-7472-3-git-send-email-yao.jin@linux.intel.com> <20170407152031.k2auigfkj7ek4suo@hirez.programming.kicks-ass.net> <20170407164834.GA4021@tassilo.jf.intel.com> <20170407172024.r66fkp4xkux5blxi@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170407172024.r66fkp4xkux5blxi@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > It's a somewhat common situation with partially JITed code, if you > > don't have an agent. You can still do a lot of useful things. > > Like what? How can you say anything about code you don't have? For example if you combine the PMU topdown measurement, and see if it's frontend bound, and then you see it has lots of forward conditionals, then dynamic basic block reordering will help. If you have lots of cross page jumps then function reordering will help. etc. > > We found it useful to have this extra information during workload > > analysis. Forward conditionals and page crossing jumps > > are indications of frontend problems. > > But you already have the exact same information in {to,from}, why would > you need to repackage information already contained? Without this patch, we don't know if it's conditional or something else. And the kernel already knows this for its filtering, so it can as well report it. Right the CROSS_* and forward backward information could be computed later. -Andi