Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753516Ab3ISKgB (ORCPT ); Thu, 19 Sep 2013 06:36:01 -0400 Received: from merlin.infradead.org ([205.233.59.134]:34930 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753123Ab3ISKgA (ORCPT ); Thu, 19 Sep 2013 06:36:00 -0400 Date: Thu, 19 Sep 2013 12:35:50 +0200 From: Peter Zijlstra To: Ingo Molnar Cc: Vince Weaver , hpa@zytor.com, linux-kernel@vger.kernel.org, adrian.hunter@intel.com, tglx@linutronix.de, linux-tip-commits@vger.kernel.org, eranian@googlemail.com Subject: Re: [PATCH] perf: Always set bit 0 in the capabilities field of 'struct perf_event_mmap_page' to 0, to maintain the ABI Message-ID: <20130919103550.GO9326@twins.programming.kicks-ass.net> References: <20130918085722.GL12926@twins.programming.kicks-ass.net> <20130918154224.GK9326@twins.programming.kicks-ass.net> <20130919081642.GL9326@twins.programming.kicks-ass.net> <20130919091452.GB14112@gmail.com> <20130919101240.GN9326@twins.programming.kicks-ass.net> <20130919102818.GA23487@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130919102818.GA23487@gmail.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2637 Lines: 67 On Thu, Sep 19, 2013 at 12:28:18PM +0200, Ingo Molnar wrote: You really don't like version fields do you ;-) > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c > index 8355c84..3ab624c 100644 > --- a/arch/x86/kernel/cpu/perf_event.c > +++ b/arch/x86/kernel/cpu/perf_event.c > @@ -1883,9 +1883,9 @@ static struct pmu pmu = { > > void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now) > { > - userpg->cap_usr_time = 0; > - userpg->cap_usr_time_zero = 0; > - userpg->cap_usr_rdpmc = x86_pmu.attr_rdpmc; > + userpg->cap_usr_time_used = 0; > + userpg->cap_usr_time_zero_used = 0; > + userpg->cap_usr_rdpmc_available = x86_pmu.attr_rdpmc; > userpg->pmc_width = x86_pmu.cntval_bits; > > if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) > @@ -1894,13 +1894,13 @@ void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now) > if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) > return; > > - userpg->cap_usr_time = 1; > + userpg->cap_usr_time_used = 1; > userpg->time_mult = this_cpu_read(cyc2ns); > userpg->time_shift = CYC2NS_SCALE_FACTOR; > userpg->time_offset = this_cpu_read(cyc2ns_offset) - now; > > if (sched_clock_stable && !check_tsc_disabled()) { > - userpg->cap_usr_time_zero = 1; > + userpg->cap_usr_time_zero_used = 1; > userpg->time_zero = this_cpu_read(cyc2ns_offset); > } > } > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > index 40a1fb8..e3514d1 100644 > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -380,10 +380,13 @@ struct perf_event_mmap_page { > union { > __u64 capabilities; > struct { > - __u64 cap_usr_time : 1, > - cap_usr_rdpmc : 1, > - cap_usr_time_zero : 1, > - cap_____res : 61; > + __u64 cap_bit0 : 1, /* Deprecated, always zero, see commit 860f085b74e9 */ > + cap_bit0_is_deprecated : 1, /* Always 1, signals that bit 0 is zero */ > + > + cap_usr_rdpmc_available : 1, /* The RDPMC instruction can be used to read counts */ > + cap_usr_time_used : 1, /* The time_* fields are uses */ > + cap_usr_time_zero_used : 1, /* The time_zero field is used */ > + cap_____res : 59; > }; > }; Would it make sense to do something like s/cap_usr/cap_user/ and drop the _available, _used postfixes? It results in different names but avoids these terribly long ones. -- 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/