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Date: Sat, 21 Feb 2009 04:39:17 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Jason Baron <jbaron@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
"Frank Ch. Eigler" <fche@...hat.com>, mingo@...e.hu,
rostedt@...dmis.org, linux-kernel@...r.kernel.org,
acme@...stprotocols.net, compudj@...stal.dyndns.org
Subject: Re: [PATCH] new irq tracer
On Fri, Feb 20, 2009 at 02:52:36PM -0500, Jason Baron wrote:
> On Wed, Feb 18, 2009 at 11:10:35PM +0100, Peter Zijlstra wrote:
> > On Wed, 2009-02-18 at 17:02 -0500, Frank Ch. Eigler wrote:
> >
> > > > I really am having a difficult time seeing the use in such narrow
> > > > tracers.
> > >
> > > Part of the problem may come from defining "tracers" as something
> > > limited to ftrace engines. Once such tracepoints are in the kernel,
> > > more powerful analytical tools may be attached to them.
> >
> > ftrace graph tracer is by far the most powerful thing I've seen, there's
> > nothing limiting about ftrace.
> >
> > What is limiting are these puny little tracers that have no real value.
> >
> > A much better purpose for these tracepoints would be augmenting data in
> > existing tracers like the graph/function/sched tracer.
> >
>
> ok...using these two tracepoints i've augmented the graph tracer to add
> a new column that prints the irq # and handler we're in, or -1
> otherwise. its a new 'funcgraph-irq' in 'trace_options', sample output:
>
>
> 1) #-1:none 2.323 us | native_apic_mem_write();
> 1) #-1:none + 21.891 us | }
> 1) #-1:none | handle_IRQ_event() {
My dream would be to see:
1) | handle_IRQ_event(29:ahci) {
But it's not possible for now, not until we have the hashtable.
Anyway, instead of having #-1:none, it would be better to have nothing
in case of user context (or softirq).
Or actually why not just an ftrace_printk when the probe is on?
Since it immediately follows the call to handle_IRQ_event, we would have the
following displayed:
1) | handle_IRQ_event() {
1) | /* 29 : ahci */
Because ftrace_printk send TRACE_PRINT entries which are displayed like this
by the function graph tracer.
It would be much more light than a whole column.
> 1) #29:ahci 1.938 us | irq_to_desc();
> 1) #29:ahci 2.626 us | runqueue_is_locked();
> 1) #29:ahci + 21.173 us | }
> .
> .
> .
> 1) #29:ahci + 32.047 us | }
> 1) #29:ahci + 43.746 us | }
> 1) #29:ahci + 51.634 us | }
> 1) #29:ahci + 61.954 us | }
> 1) #-1:none 1.014 us | runqueue_is_locked();
> 1) #-1:none | __wake_up() {
> 1) #-1:none 0.920 us | _spin_lock_irqsave();
> 1) #-1:none 1.028 us | __wake_up_common();
>
>
> This seems to work pretty well - although it does get confused by
> certain preemption events which it can't handle...I think this can make
> the logs more readable. I can probably get it working if ppl thinks its
> valuable...or have better ways of implementing it. Code is below.
>
> thanks,
>
> -Jason
>
>
> diff --git a/include/trace/irq.h b/include/trace/irq.h
> new file mode 100644
> index 0000000..ecec94a
> --- /dev/null
> +++ b/include/trace/irq.h
> @@ -0,0 +1,25 @@
> +#ifndef _TRACE_IRQ_H
> +#define _TRACE_IRQ_H
> +
> +#include <linux/interrupt.h>
> +#include <linux/tracepoint.h>
> +
> +enum {
> + IRQ_ENTRY = 0,
> + IRQ_EXIT = 1,
> +};
> +
> +struct irq_trace {
> + int type;
> + int irq;
> + char irq_name[10];
> +};
> +
> +DECLARE_TRACE(irq_entry,
> + TPPROTO(unsigned int id),
> + TPARGS(id));
> +DECLARE_TRACE(irq_exit,
> + TPPROTO(unsigned int id, irqreturn_t retval),
> + TPARGS(id, retval));
> +
> +#endif /* _TRACE_IRQ_H */
> diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
> index fdff380..34053b5 100644
> --- a/kernel/irq/handle.c
> +++ b/kernel/irq/handle.c
> @@ -18,6 +18,7 @@
> #include <linux/rculist.h>
> #include <linux/hash.h>
> #include <linux/bootmem.h>
> +#include <trace/irq.h>
>
> #include "internals.h"
>
> @@ -338,6 +339,9 @@ irqreturn_t no_action(int cpl, void *dev_id)
> return IRQ_NONE;
> }
>
> +DEFINE_TRACE(irq_entry);
> +DEFINE_TRACE(irq_exit);
> +
> /**
> * handle_IRQ_event - irq action chain handler
> * @irq: the interrupt number
> @@ -354,7 +358,9 @@ irqreturn_t handle_IRQ_event(unsigned int irq, struct irqaction *action)
> local_irq_enable_in_hardirq();
>
> do {
> + trace_irq_entry(irq);
> ret = action->handler(irq, action->dev_id);
> + trace_irq_exit(irq, ret);
> if (ret == IRQ_HANDLED)
> status |= action->flags;
> retval |= ret;
> diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
> index 627090b..58b9f7e 100644
> --- a/kernel/trace/Makefile
> +++ b/kernel/trace/Makefile
> @@ -38,5 +38,6 @@ obj-$(CONFIG_POWER_TRACER) += trace_power.o
> obj-$(CONFIG_KMEMTRACE) += kmemtrace.o
> obj-$(CONFIG_WORKQUEUE_TRACER) += trace_workqueue.o
> obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
> +obj-$(CONFIG_IRQ_TRACER) += trace_irq.o
>
> libftrace-y := ftrace.o
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index dbff020..6a34aaa 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -11,6 +11,7 @@
> #include <trace/boot.h>
> #include <trace/kmemtrace.h>
> #include <trace/power.h>
> +#include <trace/irq.h>
>
> enum trace_type {
> __TRACE_FIRST_TYPE = 0,
> @@ -33,6 +34,7 @@ enum trace_type {
> TRACE_KMEM_ALLOC,
> TRACE_KMEM_FREE,
> TRACE_POWER,
> + TRACE_IRQ,
> TRACE_BLK,
>
> __TRACE_LAST_TYPE,
> @@ -173,6 +175,11 @@ struct trace_power {
> struct power_trace state_data;
> };
>
> +struct trace_irq {
> + struct trace_entry ent;
> + struct irq_trace irq_data;
> +};
> +
> struct kmemtrace_alloc_entry {
> struct trace_entry ent;
> enum kmemtrace_type_id type_id;
> @@ -298,6 +305,7 @@ extern void __ftrace_bad_type(void);
> TRACE_GRAPH_RET); \
> IF_ASSIGN(var, ent, struct hw_branch_entry, TRACE_HW_BRANCHES);\
> IF_ASSIGN(var, ent, struct trace_power, TRACE_POWER); \
> + IF_ASSIGN(var, ent, struct trace_irq, TRACE_IRQ); \
> IF_ASSIGN(var, ent, struct kmemtrace_alloc_entry, \
> TRACE_KMEM_ALLOC); \
> IF_ASSIGN(var, ent, struct kmemtrace_free_entry, \
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index 519a0ca..4c4c777 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -10,10 +10,19 @@
> #include <linux/uaccess.h>
> #include <linux/ftrace.h>
> #include <linux/fs.h>
> +#include <trace/irq.h>
>
> #include "trace.h"
> #include "trace_output.h"
>
> +
> +struct per_cpu_irq_data {
> + int irq_num;
> + char action_str[10];
> +};
> +static struct per_cpu_irq_data cpu_irq_data[NR_CPUS];
> +static struct trace_array *graph_trace_tr;
> +
> #define TRACE_GRAPH_INDENT 2
>
> /* Flag options */
> @@ -23,6 +32,7 @@
> #define TRACE_GRAPH_PRINT_PROC 0x8
> #define TRACE_GRAPH_PRINT_DURATION 0x10
> #define TRACE_GRAPH_PRINT_ABS_TIME 0X20
> +#define TRACE_GRAPH_PRINT_IRQ 0X40
>
> static struct tracer_opt trace_opts[] = {
> /* Display overruns? (for self-debug purpose) */
> @@ -37,6 +47,8 @@ static struct tracer_opt trace_opts[] = {
> { TRACER_OPT(funcgraph-duration, TRACE_GRAPH_PRINT_DURATION) },
> /* Display absolute time of an entry */
> { TRACER_OPT(funcgraph-abstime, TRACE_GRAPH_PRINT_ABS_TIME) },
> + /* Display irq number, -1 otherwise */
> + { TRACER_OPT(funcgraph-irq, TRACE_GRAPH_PRINT_IRQ) },
> { } /* Empty entry */
> };
>
> @@ -52,10 +64,17 @@ static struct tracer_flags tracer_flags = {
>
> static int graph_trace_init(struct trace_array *tr)
> {
> + int i;
> int ret = register_ftrace_graph(&trace_graph_return,
> &trace_graph_entry);
> if (ret)
> return ret;
> + graph_trace_tr = tr;
> + for (i=0;i<NR_CPUS;i++) {
> + cpu_irq_data[i].irq_num = -1;
> + sprintf(cpu_irq_data[i].action_str, "none");
> + cpu_irq_data[i].action_str[4] = '\0';
> + }
> tracing_start_cmdline_record();
>
> return 0;
> @@ -63,6 +82,7 @@ static int graph_trace_init(struct trace_array *tr)
>
> static void graph_trace_reset(struct trace_array *tr)
> {
> + graph_trace_tr = tr;
> tracing_stop_cmdline_record();
> unregister_ftrace_graph();
> }
> @@ -110,6 +130,27 @@ print_graph_cpu(struct trace_seq *s, int cpu)
> return TRACE_TYPE_HANDLED;
> }
>
> +#define TRACE_GRAPH_IRQ_LENGTH 14
> +
> +static enum print_line_t
> +print_graph_irqnum(struct trace_seq *s, int cpu)
> +{
> + char irq_str[TRACE_GRAPH_IRQ_LENGTH];
> + int len, ret;
> +
> + len = snprintf(irq_str, TRACE_GRAPH_IRQ_LENGTH, "#%d:%s", cpu_irq_data[cpu].irq_num, cpu_irq_data[cpu].action_str);
> + ret = trace_seq_printf(s, "%s", irq_str);
> + if (!ret)
> + return TRACE_TYPE_PARTIAL_LINE;
> + while (len < TRACE_GRAPH_IRQ_LENGTH) {
> + ret = trace_seq_printf(s, " ");
> + if (!ret)
> + return TRACE_TYPE_PARTIAL_LINE;
> + len++;
> + }
> + return TRACE_TYPE_HANDLED;
> +}
> +
> #define TRACE_GRAPH_PROCINFO_LENGTH 14
>
> static enum print_line_t
> @@ -504,6 +545,13 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
> return TRACE_TYPE_PARTIAL_LINE;
> }
>
> + /* irq */
> + if (tracer_flags.val & TRACE_GRAPH_PRINT_IRQ) {
> + ret = print_graph_irqnum(s, cpu);
> + if (ret == TRACE_TYPE_PARTIAL_LINE)
> + return TRACE_TYPE_PARTIAL_LINE;
> + }
> +
> /* Proc */
> if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
> ret = print_graph_proc(s, ent->pid);
> @@ -551,6 +599,13 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
> return TRACE_TYPE_PARTIAL_LINE;
> }
>
> + /* irq */
> + if (tracer_flags.val & TRACE_GRAPH_PRINT_IRQ) {
> + ret = print_graph_irqnum(s, cpu);
> + if (ret == TRACE_TYPE_PARTIAL_LINE)
> + return TRACE_TYPE_PARTIAL_LINE;
> + }
> +
> /* Proc */
> if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
> ret = print_graph_proc(s, ent->pid);
> @@ -627,6 +682,13 @@ print_graph_comment(struct print_entry *trace, struct trace_seq *s,
> return TRACE_TYPE_PARTIAL_LINE;
> }
>
> + /* irq */
> + if (tracer_flags.val & TRACE_GRAPH_PRINT_IRQ) {
> + ret = print_graph_irqnum(s, cpu);
> + if (ret == TRACE_TYPE_PARTIAL_LINE)
> + return TRACE_TYPE_PARTIAL_LINE;
> + }
> +
> /* Proc */
> if (tracer_flags.val & TRACE_GRAPH_PRINT_PROC) {
> ret = print_graph_proc(s, ent->pid);
> @@ -699,6 +761,22 @@ print_graph_function(struct trace_iterator *iter)
> trace_assign_type(field, entry);
> return print_graph_comment(field, s, entry, iter);
> }
> + case TRACE_IRQ: {
> + struct trace_irq *field;
> + int cpu = iter->cpu;
> +
> + trace_assign_type(field, entry);
> + if (field->irq_data.type == IRQ_ENTRY) {
> + cpu_irq_data[cpu].irq_num = field->irq_data.irq;
> + strncpy(cpu_irq_data[cpu].action_str,field->irq_data.irq_name, 9);
> + cpu_irq_data[cpu].action_str[9] = '\0';
> + } else {
> + cpu_irq_data[cpu].irq_num = -1;
> + sprintf(cpu_irq_data[cpu].action_str, "none");
> + cpu_irq_data[cpu].action_str[4] = '\0';
> + }
> + return TRACE_TYPE_HANDLED;
> + }
> default:
> return TRACE_TYPE_UNHANDLED;
> }
> @@ -753,6 +831,67 @@ static void graph_trace_close(struct trace_iterator *iter)
> percpu_free(iter->private);
> }
>
> +static void probe_irq_exit(unsigned int irq, irqreturn_t retval)
> +{
> + struct ring_buffer_event *event;
> + struct trace_irq *entry;
> +
> + event = trace_buffer_lock_reserve(graph_trace_tr, TRACE_IRQ,
> + sizeof(*entry), 0, 0);
> + if (!event)
> + return;
> + entry = ring_buffer_event_data(event);
> + entry->irq_data.type = IRQ_EXIT;
> + trace_buffer_unlock_commit(graph_trace_tr, event, 0, 0);
> +}
> +
> +static void probe_irq_entry(unsigned int id)
> +{
> + struct ring_buffer_event *event;
> + struct trace_irq *entry;
> + struct irq_desc *desc;
> +
> + event = trace_buffer_lock_reserve(graph_trace_tr, TRACE_IRQ,
> + sizeof(*entry), 0, 0);
> + if (!event)
> + return;
> + entry = ring_buffer_event_data(event);
> + entry->irq_data.irq = id;
> + entry->irq_data.type = IRQ_ENTRY;
> + desc = irq_to_desc(id);
> + strncpy(entry->irq_data.irq_name, desc->action->name, 9);
> + entry->irq_data.irq_name[9] = '\0';
> + trace_buffer_unlock_commit(graph_trace_tr, event, 0, 0);
> +}
> +
> +static int graph_trace_set_flag(u32 old_flags, u32 bit, int set)
> +{
> + int ret = 0;
> +
> + if (bit == TRACE_GRAPH_PRINT_IRQ) {
> + /* do nothing if already set */
> + //if (!!set == !!(func_flags.val & TRACE_GRAPH_PRINT_IRQ))
> + // return 0;
> + if (set) {
> + ret = register_trace_irq_entry(probe_irq_entry);
> + if (ret) {
> + pr_info("irq trace: irq entry tracepoint failed to register\n");
> + return ret;
> + }
> + ret = register_trace_irq_exit(probe_irq_exit);
> + if (ret) {
> + pr_info("irq trace: irq exit tracepoint failed to register\n");
> + unregister_trace_irq_entry(probe_irq_entry);
> + return ret;
> + }
> + } else {
> + unregister_trace_irq_entry(probe_irq_entry);
> + unregister_trace_irq_exit(probe_irq_exit);
> + }
> + }
> + return ret;
> +}
> +
> static struct tracer graph_trace __read_mostly = {
> .name = "function_graph",
> .open = graph_trace_open,
> @@ -762,6 +901,7 @@ static struct tracer graph_trace __read_mostly = {
> .print_line = print_graph_function,
> .print_header = print_graph_headers,
> .flags = &tracer_flags,
> + .set_flag = graph_trace_set_flag,
> #ifdef CONFIG_FTRACE_SELFTEST
> .selftest = trace_selftest_startup_function_graph,
> #endif
>
--
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