Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759465Ab3EGBfd (ORCPT ); Mon, 6 May 2013 21:35:33 -0400 Received: from ozlabs.org ([203.10.76.45]:43437 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757670Ab3EGBfa (ORCPT ); Mon, 6 May 2013 21:35:30 -0400 From: Michael Neuling To: Peter Zijlstra , eranian@google.com cc: Linux PPC dev , linux-kernel@vger.kernel.org, michael@ellerman.id.au, Anshuman Khandual X-GPG-Fingerprint: 9B25 DC2A C58D 2C8D 47C2 457E 0887 E86F 32E6 BE16 X-GPG-Fingerprint: 9365 87D7 A7EF 4721 420B 91D9 CD5B 874B EAC1 B3F5 MIME-Version: 1.0 Subject: Invalid perf_branch_entry.to entries question X-Mailer: MH-E 8.2; nmh 1.5; GNU Emacs 23.4.1 Date: Tue, 07 May 2013 11:35:28 +1000 Message-ID: <25394.1367890528@ale.ozlabs.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 919 Lines: 26 Peter & Stephane, We are plumbing the POWER8 Branch History Rolling Buffer (BHRB) into struct perf_branch_entry. Sometimes on POWER8 we may not be able to fill out the "to" address. We initially thought of just making this 0, but it's feasible that this could be a valid address to branch to. The other logical value to indicate an invalid entry would be all 1s which is not possible (on POWER at least). Do you guys have a preference as to what we should use as an invalid entry? This would have some consequences for the userspace tool also. The alternative would be to add a flag alongside mispred/predicted to indicate the validity of the "to" address. Mikey -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/