From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754910AbaKSGBO (ORCPT ); Wed, 19 Nov 2014 01:01:14 -0500 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:57527 "EHLO lgemrelse6q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750939AbaKSGBN (ORCPT ); Wed, 19 Nov 2014 01:01:13 -0500 X-Original-SENDERIP: 10.177.222.235 X-Original-MAILFROM: namhyung@gmail.com From: Namhyung Kim To: "Liang\, Kan" Cc: "acme\@kernel.org" , "jolsa\@redhat.com" , "a.p.zijlstra\@chello.nl" , "eranian\@google.com" , "linux-kernel\@vger.kernel.org" , "mingo\@redhat.com" , "paulus\@samba.org" , "ak\@linux.intel.com" Subject: Re: [PATCH V3 3/3] perf tools: Construct LBR call chain References: <1415972652-17310-1-git-send-email-kan.liang@intel.com> <1415972652-17310-4-git-send-email-kan.liang@intel.com> <87d28lqb35.fsf@sejong.aot.lge.com> <37D7C6CF3E00A74B8858931C1DB2F077016711F9@SHSMSX103.ccr.corp.intel.com> Date: Wed, 19 Nov 2014 15:01:10 +0900 In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F077016711F9@SHSMSX103.ccr.corp.intel.com> (Kan Liang's message of "Tue, 18 Nov 2014 14:01:06 +0000") Message-ID: <874mtvraop.fsf@sejong.aot.lge.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 18 Nov 2014 14:01:06 +0000, Kan Liang wrote: >> On Fri, 14 Nov 2014 08:44:12 -0500, kan liang wrote: >> > + /* LBR only affects the user callchain */ >> > + if (i != chain_nr) { >> > + struct branch_stack *lbr_stack = sample- >> >branch_stack; >> > + int lbr_nr = lbr_stack->nr; >> > + /* >> > + * LBR callstack can only get user call chain. >> > + * The mix_chain_nr is kernel call chain >> > + * number plus LBR user call chain number. >> > + * i is kernel call chain number, >> > + * 1 is PERF_CONTEXT_USER, >> > + * lbr_nr + 1 is the user call chain number. >> > + * For details, please refer to the comments >> > + * in callchain__printf >> > + */ >> > + int mix_chain_nr = i + 1 + lbr_nr + 1; >> > + >> > + if (mix_chain_nr > PERF_MAX_STACK_DEPTH) { >> > + pr_warning("corrupted callchain. >> skipping...\n"); >> > + return 0; >> > + } >> >> I'm not sure whether this is really a corrupted callchain. If a single chain is >> greater than the max it should be corrupted, but we're now summing up >> with other values.. >> >> What about checking callchain_nr and lbr_nr separately or mix_nr with >> 2*max? > > The lbr_nr max is 16. I will change it to max+16. Shouldn't it be 18 (16 + 1 + 1) at least? Thanks, Namhyung