Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753515Ab1E1N0p (ORCPT ); Sat, 28 May 2011 09:26:45 -0400 Received: from aspirin.dii.utk.edu ([160.36.0.81]:36819 "EHLO aspirin.dii.utk.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753373Ab1E1N0o (ORCPT ); Sat, 28 May 2011 09:26:44 -0400 Date: Sat, 28 May 2011 09:26:02 -0400 (EDT) From: Vince Weaver To: Peter Zijlstra cc: linux-kernel@vger.kernel.org, mingo@elte.hu, paulus@samba.org, acme@redhat.com, torvalds@linux-foundation.org Subject: Re: perf: definition of a "regression" In-Reply-To: <1306578144.1200.1150.camel@twins> Message-ID: References: <1306182141.2497.5.camel@laptop> <1306233036.2497.15.camel@laptop> <1306578144.1200.1150.camel@twins> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1396 Lines: 31 On Sat, 28 May 2011, Peter Zijlstra wrote: > On Fri, 2011-05-27 at 23:38 -0400, Vince Weaver wrote: > > on that note (and while trying to document exactly what the ioctls do) it > > seems that a PERF_EVENT_IOC_REFRESH with an argument of anything higher > > than one does not work on kernels 2.6.36 and newer. The behavior acts > > as if 1 was passed, even if you pass in, say, 3. > > Urgh, no that should definitely work. Thanks for the test-case, I'll > work on that (probably not until Monday though, but who knows). So wait, the two regressions I found in 2.6.37 are WONTFIX because they are too old, even though they break existing userspace code? And this older regression in 2.6.36 is going to be fixed, even though perf, PAPI, and libpfm4 don't trigger the buggy functionality at all? I think it's time to redefine the PERF_EVENT_IOC_REFRESH ioctl to just refresh once (as that's what it actually does on 2.6.36 - 2.6.39) and if we need to refresh multiple we should add a new PERF_EVENT_IOC_REFRESH_COUNT ioctl. I know I am being difficult, but the perf-event ABI is a mess to program for in a backward compatible fashion. Vince -- 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/