Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752487AbdFZWv6 (ORCPT ); Mon, 26 Jun 2017 18:51:58 -0400 Received: from mga06.intel.com ([134.134.136.31]:3250 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752148AbdFZWux (ORCPT ); Mon, 26 Jun 2017 18:50:53 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.39,397,1493708400"; d="scan'208";a="1187235767" From: Tom Zanussi To: rostedt@goodmis.org Cc: tglx@linutronix.de, mhiramat@kernel.org, namhyung@kernel.org, vedang.patel@intel.com, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, Tom Zanussi Subject: [PATCH 32/32] tracing: Add a clock attribute for hist triggers Date: Mon, 26 Jun 2017 17:49:33 -0500 Message-Id: <4081eb1783f9ea0c1ec92ada1bd22a9246b6472a.1498510759.git.tom.zanussi@linux.intel.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3761 Lines: 116 The default clock if timestamps are used in a histogram is "global". If timestamps aren't used, the clock is irrelevant. Use the "clock=" param only if you want to override the default "global" clock for a histogram with timestamps. Signed-off-by: Tom Zanussi --- Documentation/trace/events.txt | 9 +++++++++ kernel/trace/trace_events_hist.c | 34 +++++++++++++++++++++++++++++++--- 2 files changed, 40 insertions(+), 3 deletions(-) diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt index 888907c..20e4fd4 100644 --- a/Documentation/trace/events.txt +++ b/Documentation/trace/events.txt @@ -2173,6 +2173,15 @@ features have been added to the hist trigger support: default it is in units of nanoseconds; appending '.usecs' to a common_timestamp field changes the units to microseconds. +A note on inter-event timestamps: If $common_timestamp is used in a +histogram, the trace buffer is automatically switched over to using +absolute timestamps and the "global" trace clock, in order to avoid +bogus timestamp differences with other clocks that aren't coherent +across CPUs. This can be overriden by specifying one of the other +trace clocks instead, using the "clock=XXX" hist trigger attribute, +where XXX is any of the clocks listed in the tracing/trace_clock +pseudo-file. + These features are decribed in more detail in the following sections. 6.3.1 Histogram Variables diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 06049f8..af508a3 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -233,6 +233,7 @@ struct hist_trigger_attrs { char *vals_str; char *sort_key_str; char *name; + char *clock; bool pause; bool cont; bool clear; @@ -1586,6 +1587,7 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs) kfree(attrs->sort_key_str); kfree(attrs->keys_str); kfree(attrs->vals_str); + kfree(attrs->clock); kfree(attrs); } @@ -1625,7 +1627,16 @@ static int parse_assignment(char *str, struct hist_trigger_attrs *attrs) attrs->sort_key_str = kstrdup(str, GFP_KERNEL); else if (strncmp(str, "name=", strlen("name=")) == 0) attrs->name = kstrdup(str, GFP_KERNEL); - else if (strncmp(str, "size=", strlen("size=")) == 0) { + else if (strncmp(str, "clock=", strlen("clock=")) == 0) { + strsep(&str, "="); + if (!str) { + ret = -EINVAL; + goto out; + } + + str = strstrip(str); + attrs->clock = kstrdup(str, GFP_KERNEL); + } else if (strncmp(str, "size=", strlen("size=")) == 0) { int map_bits = parse_map_size(str); if (map_bits < 0) { @@ -1688,6 +1699,12 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str) goto free; } + if (!attrs->clock) { + attrs->clock = kstrdup("global", GFP_KERNEL); + if (!attrs->clock) + goto free; + } + return attrs; free: destroy_hist_trigger_attrs(attrs); @@ -4437,6 +4454,8 @@ static int event_hist_trigger_print(struct seq_file *m, seq_puts(m, ".descending"); } seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits)); + if (hist_data->enable_timestamps) + seq_printf(m, ":clock=%s", hist_data->attrs->clock); print_actions_spec(m, hist_data); @@ -4702,10 +4721,19 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops, goto out; } - ret++; + if (hist_data->enable_timestamps) { + char *clock = hist_data->attrs->clock; + + ret = tracing_set_clock(file->tr, hist_data->attrs->clock); + if (ret) { + hist_err("Couldn't set trace_clock: ", clock); + goto out; + } - if (hist_data->enable_timestamps) tracing_set_time_stamp_abs(file->tr, true); + } + + ret++; out: return ret; } -- 1.9.3