From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751622Ab3CNT5H (ORCPT ); Thu, 14 Mar 2013 15:57:07 -0400 Received: from service87.mimecast.com ([91.220.42.44]:59949 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751271Ab3CNT5G convert rfc822-to-8bit (ORCPT ); Thu, 14 Mar 2013 15:57:06 -0400 Message-ID: <1363291021.3100.144.camel@hornet> Subject: Re: [RFC] perf: need to expose sched_clock to correlate user samples with kernel samples From: Pawel Moll To: Stephane Eranian Cc: Peter Zijlstra , John Stultz , Thomas Gleixner , LKML , "mingo@elte.hu" , Paul Mackerras , Anton Blanchard , Will Deacon , "ak@linux.intel.com" , Pekka Enberg , Steven Rostedt , Robert Richter Date: Thu, 14 Mar 2013 19:57:01 +0000 In-Reply-To: References: <1350408232.2336.42.camel@laptop> <1359728280.8360.15.camel@hornet> <51118797.9080800@linaro.org> <5123C3AF.8060100@linaro.org> <1361356160.10155.22.camel@laptop> <51285BF1.2090208@linaro.org> <1361801441.4007.40.camel@laptop> X-Mailer: Evolution 3.6.2-0ubuntu0.1 Mime-Version: 1.0 X-OriginalArrivalTime: 14 Mar 2013 19:57:02.0002 (UTC) FILETIME=[1829C920:01CE20EE] X-MC-Unique: 113031419570305201 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2013-03-14 at 15:34 +0000, Stephane Eranian wrote: > > Well, the timestamps themselves are already exposed to userspace > > through the ftrace and perf data logs. All people want is to add > > secondary data stream in the same time-line. > > > I agree with Peter on this. The timestamps are already visible. > All we need is the ability to generate them for another user-level > level data stream. Ok, how about the code below? I must say I have some doubts about the resolution, as there seem to be no generic way of figuring it out for the sched_clock (the arch/arm/kernel/sched_clock.c is actually calculating it, but than just prints it out and nothing more). And, to summarize, we went through 3 ideas: 1. ioctl() - http://article.gmane.org/gmane.linux.kernel/1433933 2. syscall - http://article.gmane.org/gmane.linux.kernel/1437057 3. POSIX clock - below John also suggested that maybe the perf could use CLOCK_MONOTONIC_RAW instead of local/sched_clock(). How about a final decision? Regards Pawel 8<-------------------- >>From c986492d38156f1fc25ab3182f0a494bb13389ce Mon Sep 17 00:00:00 2001 From: Pawel Moll Date: Thu, 14 Mar 2013 19:49:09 +0000 Subject: [PATCH] perf: POSIX CLOCK_PERF to report current time value To co-relate user space events with the perf events stream a current (as in: "what time(stamp) is it now?") time value must be made available. This patch adds a POSIX clock returning the perf_clock() value and accesible from userspace: #include struct timespec ts; clock_gettime(CLOCK_PERF, &ts); Signed-off-by: Pawel Moll --- include/uapi/linux/time.h | 1 + kernel/events/core.c | 20 ++++++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/include/uapi/linux/time.h b/include/uapi/linux/time.h index 0d3c0ed..cea16b0 100644 --- a/include/uapi/linux/time.h +++ b/include/uapi/linux/time.h @@ -54,6 +54,7 @@ struct itimerval { #define CLOCK_BOOTTIME 7 #define CLOCK_REALTIME_ALARM 8 #define CLOCK_BOOTTIME_ALARM 9 +#define CLOCK_PERF 10 /* * The IDs of various hardware clocks: diff --git a/kernel/events/core.c b/kernel/events/core.c index b0cd865..81ca459 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -37,6 +37,7 @@ #include #include #include +#include #include "internal.h" @@ -209,6 +210,19 @@ static inline u64 perf_clock(void) return local_clock(); } +static int perf_posix_clock_getres(const clockid_t which_clock, + struct timespec *tp) +{ + *tp = ns_to_timespec(TICK_NSEC); + return 0; +} + +static int perf_posix_clock_get(clockid_t which_clock, struct timespec *tp) +{ + *tp = ns_to_timespec(perf_clock()); + return 0; +} + static inline struct perf_cpu_context * __get_cpu_context(struct perf_event_context *ctx) { @@ -7391,6 +7405,10 @@ perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) void __init perf_event_init(void) { + struct k_clock perf_posix_clock = { + .clock_getres = perf_posix_clock_getres, + .clock_get = perf_posix_clock_get, + }; int ret; idr_init(&pmu_idr); @@ -7407,6 +7425,8 @@ void __init perf_event_init(void) ret = init_hw_breakpoint(); WARN(ret, "hw_breakpoint initialization failed with: %d", ret); + posix_timers_register_clock(CLOCK_PERF, &perf_posix_clock); + /* do not patch jump label more than once per second */ jump_label_rate_limit(&perf_sched_events, HZ); -- 1.7.10.4