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Date: Thu, 28 Nov 2013 18:50:24 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: David Ahern <dsahern@...il.com>
Cc: acme@...stprotocols.net, linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...nel.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Mike Galbraith <efault@....de>, Jiri Olsa <jolsa@...hat.com>,
Stephane Eranian <eranian@...gle.com>,
Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH 6/8] perf sched: Introduce timehist command
On Mon, 18 Nov 2013 13:32:49 -0700, David Ahern wrote:
> 'perf sched timehist' provides an analysis of scheduling events.
>
> Example usage:
> perf sched record -- sleep 1
> perf sched timehist
>
> By default it shows the individual schedule events, including the time between
> sched-in events for the task, the task scheduling delay (time between wakeup
> and actually running) and run time for the task:
>
> time cpu task name[tid/pid] b/n time sch delay run time
> --------------- ---- -------------------- --------- --------- ---------
> 79371.874569 [11] gcc[31949] 0.000014 0.000000 0.001148
> 79371.874591 [10] gcc[31951] 0.000000 0.000000 0.000024
> 79371.874603 [10] migration/10[59] 0.003350 0.000004 0.000011
> 79371.874604 [11] <idle> 0.001148 0.000000 0.000035
> 79371.874723 [05] <idle> 0.000016 0.000000 0.001383
> 79371.874746 [05] gcc[31949] 0.000153 0.000078 0.000022
> ...
>
> If callchains were recorded they are appended to the line with a default stack depth of 5:
>
> 79371.874569 [11] gcc[31949] 0.000014 0.000000 0.001148 wait_for_completion_killable do_fork sys_vfork stub_vfork __vfork
> 79371.874591 [10] gcc[31951] 0.000000 0.000000 0.000024 __cond_resched _cond_resched wait_for_completion stop_one_cpu sched_exec
> 79371.874603 [10] migration/10[59] 0.003350 0.000004 0.000011 smpboot_thread_fn kthread ret_from_fork
> 79371.874604 [11] <idle> 0.001148 0.000000 0.000035 cpu_startup_entry start_secondary
> 79371.874723 [05] <idle> 0.000016 0.000000 0.001383 cpu_startup_entry start_secondary
> 79371.874746 [05] gcc[31949] 0.000153 0.000078 0.000022 do_wait sys_wait4 system_call_fastpath __GI___waitpid
>
> --no-call-graph can be used to not show the callchains. --max-stack is used
> to control the number of frames shown (default of 5). -x/--excl options can
> be used to collapse redundant callchains to get more relevant data on screen.
>
> Similar to perf-trace -s and -S can be used to dump a statistical summary
> without or with events (respectively). Statistics include min run time,
> average run time and max run time. Stats are also shown for run time by
> cpu.
>
> The cpu-visual option provides a visual aid for sched switches by cpu:
> ...
> 79371.874569 [11] s gcc[31949] 0.000014 0.000000 0.001148
> 79371.874591 [10] s gcc[31951] 0.000000 0.000000 0.000024
> 79371.874603 [10] s migration/10[59] 0.003350 0.000004 0.000011
> 79371.874604 [11] i <idle> 0.001148 0.000000 0.000035
> 79371.874723 [05] i <idle> 0.000016 0.000000 0.001383
> 79371.874746 [05] s gcc[31949] 0.000153 0.000078 0.000022
> ...
>
> Additional options:
> - -w option can be used to include a dump of wakeup events
> - -c comm to only display events and stats for the given comm (csv list)
> - -p/-t to only display events and stats for given pid/tid (csv list)
Looks like a very nice feature. I haven't read the whole patch yet but
just want some comments. More will come later. :)
[SNIP]
> +static inline void printf_nsecs(unsigned long long nsecs, int width_sec)
> +{
> + unsigned long secs;
> + unsigned long usecs;
> +
> + secs = nsecs / NSECS_PER_SEC;
> + nsecs -= secs * NSECS_PER_SEC;
> + usecs = nsecs / NSECS_PER_USEC;
> + printf("%*lu.%06lu ", width_sec, secs, usecs);
> +}
It seems very similar to what timehist_time_str() does. Better to
factor out?
[SNIP]
> +static unsigned int comm_width = 20;
> +
> +static char *timehist_get_commstr(struct thread *thread)
> +{
> + static char str[32];
> + const char *comm = thread__comm_str(thread);
> + pid_t tid = thread->tid;
> + pid_t pid = thread->pid_;
> + unsigned int n;
> +
> + if (pid == 0)
> + scnprintf(str, sizeof(str), "%s", comm);
> +
> + else if (tid != pid)
> + scnprintf(str, sizeof(str), "%s[%d/%d]", comm, tid, pid);
> +
> + else
> + scnprintf(str, sizeof(str), "%s[%d]", comm, tid);
> +
> + n = strlen(str);
Why not just using return value of scnprintf()?
> + if (n > comm_width)
> + comm_width = n;
> +
> + return str;
> +}
> +
> +static void timehist_header(struct perf_sched *sched)
> +{
> + u32 max_cpus = sched->max_cpu;
> + u32 i, j;
> +
> + printf("%15s %-4s", "time", "cpu");
> +
> + if (sched->show_cpu_visual && max_cpus) {
> + printf(" ");
> + for (i = 0, j = 0; i < max_cpus; ++i) {
> + printf("%x", j++);
> + if (j > 15)
> + j = 0;
> + }
> + printf(" ");
> + }
> +
> + printf(" %-20s %9s %9s %9s",
> + "task name[tid/pid]", "b/n time", "sch delay", "run time");
> +
> + if (sched->show_wakeups)
> + printf(" %-20s", "wakeup");
> +
> + printf("\n");
> +
> + printf("%15s %4s", "---------------", "----");
You might want to use "%.15s" and graph_dotted_line.
> +
> + if (sched->show_cpu_visual && max_cpus) {
> + printf(" ");
> + for (i = 0; i < max_cpus; ++i)
> + printf("-");
> + printf(" ");
> + }
> +
> + printf(" %20s %9s %9s %9s",
> + "--------------------", "---------", "---------", "---------");
Ditto.
> +
> + if (sched->show_wakeups)
> + printf(" %20s", "--------------------");
Ditto.
> +
> + printf("\n");
> +}
> +
> +static char *timehist_time_str(char *tstr, int len, u64 t)
> +{
> + unsigned long secs, usecs;
> + unsigned long long nsecs;
> +
> + nsecs = t;
> + secs = nsecs / NSECS_PER_SEC;
> + nsecs -= secs * NSECS_PER_SEC;
> + usecs = nsecs / NSECS_PER_USEC;
> + snprintf(tstr, len, "%5lu.%06lu", secs, usecs);
> +
> + return tstr;
> +}
See above.
> +
> +static void timehist_print_sample(struct perf_sched *sched,
> + union perf_event *event,
> + struct perf_evsel *evsel,
> + struct perf_sample *sample,
> + struct thread *thread,
> + struct machine *machine)
> +{
> + struct thread_runtime *tr = thread__priv(thread);
> + char tstr[64];
> + u32 max_cpus = sched->max_cpu;
> +
> + printf("%15s ", timehist_time_str(tstr, sizeof(tstr), sample->time));
> +
> + printf("[%02d] ", sample->cpu);
> +
> + if (sched->show_cpu_visual && max_cpus) {
> + u32 i;
> + char c;
> + for (i = 0; i < max_cpus; ++i) {
> + if (i == sample->cpu)
> + c = (thread->tid == 0) ? 'i' : 's';
It'd better explaining what the 'i' and 's' mean..
> + else
> + c = ' ';
> + printf("%c", c);
> + }
> + printf(" ");
> + }
> +
> + printf("%-*s ", comm_width, timehist_get_commstr(thread));
> +
> + printf_nsecs(tr->dt_between, 2);
> + printf_nsecs(tr->dt_delay, 2);
> + printf_nsecs(tr->dt_run, 2);
> +
> + if (sched->show_wakeups)
> + printf(" %-*s ", comm_width, "");
> +
> + perf_evsel__print_ip(evsel, event, sample, machine,
> + PRINT_IP_OPT_SYM | PRINT_IP_OPT_ONELINE,
> + sched->max_stack);
> +
> + printf("\n");
> +}
[SNIP]
> +static void free_idle_threads(void)
> +{
> + int i;
> +
> + if (idle_threads == NULL)
> + return;
> +
> + for (i = 0; i <= idle_max_cpu; ++i)
> + free(idle_threads[i]);
Doesn't it need to be thread__delete(idle_threads[i]) ?
Thanks,
Namhyung
> +
> + free(idle_threads);
> +}
--
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