From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934039AbaKMUP1 (ORCPT ); Thu, 13 Nov 2014 15:15:27 -0500 Received: from one.firstfloor.org ([193.170.194.197]:38380 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933146AbaKMUP0 (ORCPT ); Thu, 13 Nov 2014 15:15:26 -0500 Date: Thu, 13 Nov 2014 21:15:24 +0100 From: Andi Kleen To: Arnaldo Carvalho de Melo Cc: Andi Kleen , jolsa@redhat.com, linux-kernel@vger.kernel.org, namhyung@kernel.org, Andi Kleen Subject: Re: [PATCH 02/10] perf, tools: Support handling complete branch stacks as histograms Message-ID: <20141113201524.GU12538@two.firstfloor.org> References: <1415844328-4884-1-git-send-email-andi@firstfloor.org> <1415844328-4884-3-git-send-email-andi@firstfloor.org> <20141113191417.GC3612@kernel.org> <20141113195208.GS12538@two.firstfloor.org> <20141113200833.GI3612@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141113200833.GI3612@kernel.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 13, 2014 at 05:08:33PM -0300, Arnaldo Carvalho de Melo wrote: > Em Thu, Nov 13, 2014 at 08:52:08PM +0100, Andi Kleen escreveu: > > On Thu, Nov 13, 2014 at 04:14:17PM -0300, Arnaldo Carvalho de Melo wrote: > > > Em Wed, Nov 12, 2014 at 06:05:20PM -0800, Andi Kleen escreveu: > > > > +static int remove_loops(struct branch_entry *l, int nr) > > > > +{ > > > > + int i, j, off; > > > > + unsigned char chash[CHASHSZ]; > > > > + > > > > + memset(chash, NO_ENTRY, sizeof(chash)); > > > > + > > > > + BUG_ON(nr >= 256); > > > > > > What is wrong with return -1 and propagating the error, so that the user > > > is informed if the data being processed is bogus, stop processing with a > > > warning or continue processing if finding the next valid record is > > > possible? > > > > The error doesn't depend on the record. There is a check for the record > > being < 127 in front of this. This is merely to catch that > > if someone increases PERF_MAX_BRANCH_DEPTH to below 255 they need > > to increase the type of the hash table from u8. > > Ok, so this would be better as a BUILD_BUG_ON? Yes that should work. -Andi > > Like: > > #define CHASHSZ 127 > #define CHASHBITS 7 > #define NO_ENTRY 0xff > > #define PERF_MAX_BRANCH_DEPTH 127 > > /* Remove loops. */ > static int remove_loops(struct branch_entry *l, int nr) > { > int i, j, off; > unsigned char chash[CHASHSZ]; > > memset(chash, NO_ENTRY, sizeof(chash)); > > /* Change the type of the chash table, u8 is not enough now */ > BUILD_BUG_ON(PERF_MAX_BRANCH_DEPTH >= 256); > for (i = 0; i < nr; i++) { > int h = hash_64(l[i].from, CHASHBITS) % CHASHSZ; > > ------------------------------------- > > - Arnaldo > -- ak@linux.intel.com -- Speaking for myself only.