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Date: Sat, 27 Feb 2010 09:55:58 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Tim Bird <tim.bird@...sony.com>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH][RFC] ftrace: add tracing_thresh support to
function_graph tracer (v3)
On Fri, Feb 26, 2010 at 08:32:35PM -0500, Steven Rostedt wrote:
> Frederic,
>
> Can you take look at this patch, and if you agree, can you give it your
> ACK? Applying this on top of my pull request gives a nice output:
>
> [root@...hel51 tracing]# echo 300 > tracing_thresh
> [root@...hel51 tracing]# cat trace | head -30
> # tracer: function_graph
> #
> # CPU DURATION FUNCTION CALLS
> # | | | | | | |
> 1) ! 3630.044 us | } (__dentry_open)
> 1) ! 3632.456 us | } (nameidata_to_filp)
> 1) ! 3685.980 us | } (do_filp_open)
> 1) ! 3701.625 us | } (do_sys_open)
> 1) ! 3702.830 us | } (sys_open)
> ------------------------------------------
> 1) bash-4190 => events/-16
> ------------------------------------------
>
> 1) ! 4152.329 us | } (schedule)
> ------------------------------------------
> 1) events/-16 => bash-4190
> ------------------------------------------
>
> 1) ! 461.230 us | } (_raw_spin_unlock_irqrestore)
> 1) ! 466.865 us | } (tty_ldisc_try)
> 1) ! 468.948 us | } (tty_ldisc_ref_wait)
> 0) ! 333.541 us | } (walk_tg_tree)
> 0) ! 339.638 us | } (update_shares)
> 0) ! 488.176 us | } (rebalance_domains)
> 0) ! 490.382 us | } (run_rebalance_domains)
> 0) ! 532.406 us | } (__do_softirq)
> 0) ! 536.246 us | } (do_softirq)
> 0) ! 540.842 us | } (irq_exit)
> 0) ! 593.286 us | } (smp_apic_timer_interrupt)
Cool!
>
>
>
> (note, I forgot to update the changelog, I'll do that next)
>
> -- Steve
>
>
> commit c020a9a11ec44e0c81f1aa16781d2d42c6c5e560
> Author: Tim Bird <tim.bird@...sony.com>
> Date: Thu Feb 25 15:36:43 2010 -0800
>
> ftrace: add tracing_thresh support to function_graph tracer (v3)
>
> Add support for tracing_thresh to the function_graph tracer. This
> version of this feature isolates the checks into new entry and
> return functions, to avoid adding more conditional code into the
> main function_graph paths.
>
> Also, add support for specifying tracing_thresh on the kernel
> command line. When used like so: "tracing_thresh=200 ftrace=function_graph"
> this can be used to analyse system startup. It is important to disable
> tracing soon after boot, in order to avoid losing the trace data.
>
> Note: the elimination of 'notrace' in the definition of '__init'
> may be controversial. This can be removed, or made conditional,
> if it's a bit too scary, but it worked OK for me. Tracing during
> kernel startup still works, just with no visibility of routines
> declared __init.
>
> Signed-off-by: Tim Bird <tim.bird@...sony.com>
> LKML-Reference: <4B87098B.4040308@...sony.com>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 032c57c..34ead59 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -374,6 +374,21 @@ static int __init set_buf_size(char *str)
> }
> __setup("trace_buf_size=", set_buf_size);
>
> +static int __init set_tracing_thresh(char *str)
> +{
> + unsigned long threshhold;
> + int ret;
> +
> + if (!str)
> + return 0;
> + ret = strict_strtoul(str, 0, &threshhold);
> + if (ret < 0)
> + return 0;
> + tracing_thresh = threshhold * 1000;
> + return 1;
> +}
> +__setup("tracing_thresh=", set_tracing_thresh);
> +
> unsigned long nsecs_to_usecs(unsigned long nsecs)
> {
> return nsecs / 1000;
> @@ -579,9 +594,10 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
> static arch_spinlock_t ftrace_max_lock =
> (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
>
> +unsigned long __read_mostly tracing_thresh;
> +
> #ifdef CONFIG_TRACER_MAX_TRACE
> unsigned long __read_mostly tracing_max_latency;
> -unsigned long __read_mostly tracing_thresh;
>
> /*
> * Copy the new maximum trace into the separate maximum-trace
> @@ -4248,10 +4264,10 @@ static __init int tracer_init_debugfs(void)
> #ifdef CONFIG_TRACER_MAX_TRACE
> trace_create_file("tracing_max_latency", 0644, d_tracer,
> &tracing_max_latency, &tracing_max_lat_fops);
> +#endif
>
> trace_create_file("tracing_thresh", 0644, d_tracer,
> &tracing_thresh, &tracing_max_lat_fops);
> -#endif
>
> trace_create_file("README", 0444, d_tracer,
> NULL, &tracing_readme_fops);
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index fd05bca..1bc8cd1 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -396,9 +396,10 @@ extern int process_new_ksym_entry(char *ksymname, int op, unsigned long addr);
>
> extern unsigned long nsecs_to_usecs(unsigned long nsecs);
>
> +extern unsigned long tracing_thresh;
> +
> #ifdef CONFIG_TRACER_MAX_TRACE
> extern unsigned long tracing_max_latency;
> -extern unsigned long tracing_thresh;
>
> void update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu);
> void update_max_tr_single(struct trace_array *tr,
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index e998a82..aaf580c 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -237,6 +237,14 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
> return ret;
> }
>
> +int trace_graph_thresh_entry(struct ftrace_graph_ent *trace)
> +{
> + if (tracing_thresh)
> + return 1;
> + else
> + return trace_graph_entry(trace);
> +}
> +
> static void __trace_graph_return(struct trace_array *tr,
> struct ftrace_graph_ret *trace,
> unsigned long flags,
> @@ -290,13 +298,26 @@ void set_graph_array(struct trace_array *tr)
> smp_mb();
> }
>
> +void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
> +{
> + if (tracing_thresh &&
> + (trace->rettime - trace->calltime < tracing_thresh))
> + return;
> + else
> + trace_graph_return(trace);
> +}
> +
> static int graph_trace_init(struct trace_array *tr)
> {
> int ret;
>
> set_graph_array(tr);
> - ret = register_ftrace_graph(&trace_graph_return,
> - &trace_graph_entry);
> + if (tracing_thresh)
> + ret = register_ftrace_graph(&trace_graph_thresh_return,
> + &trace_graph_thresh_entry);
> + else
> + ret = register_ftrace_graph(&trace_graph_return,
> + &trace_graph_entry);
> if (ret)
> return ret;
> tracing_start_cmdline_record();
>
>
The parts that deal with the tracing_thresh file and the output
seem missing?
Other than that this all looks good to me.
Thanks.
Acked-by: Frederic Weisbecker <fweisbec@...il.com>
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