linux-kernel - Re: [RFC v3 01/17] perf kwork: New tool

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Date:   Wed, 27 Jul 2022 16:33:32 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Yang Jihong <yangjihong1@...wei.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Paul Clarke <pc@...ibm.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>
Subject: Re: [RFC v3 01/17] perf kwork: New tool

Hello,

On Fri, Jul 8, 2022 at 6:53 PM Yang Jihong <yangjihong1@...wei.com> wrote:
>
> The perf-kwork tool is used to trace time properties of kernel work
> (such as irq, softirq, and workqueue), including runtime, latency,
> and timehist, using the infrastructure in the perf tools to allow
> tracing extra targets.
>
> This is the first commit to reuse perf_record framework code to
> implement a simple record function, kwork is not supported currently.
>
> Test cases:
>
>   # perf
>
>    usage: perf [--version] [--help] [OPTIONS] COMMAND [ARGS]
>
>    The most commonly used perf commands are:
>   <SNIP>
>      iostat          Show I/O performance metrics
>      kallsyms        Searches running kernel for symbols
>      kmem            Tool to trace/measure kernel memory properties
>      kvm             Tool to trace/measure kvm guest os
>      kwork           Tool to trace/measure kernel work properties (latencies)
>      list            List all symbolic event types
>      lock            Analyze lock events
>      mem             Profile memory accesses
>      record          Run a command and record its profile into perf.data
>   <SNIP>
>    See 'perf help COMMAND' for more information on a specific command.
>
>   # perf kwork
>
>    Usage: perf kwork [<options>] {record}
>
>       -D, --dump-raw-trace  dump raw trace in ASCII
>       -f, --force           don't complain, do it
>       -k, --kwork <kwork>   list of kwork to profile
>       -v, --verbose         be more verbose (show symbol address, etc)
>
>   # perf kwork record -- sleep 1
>   [ perf record: Woken up 0 times to write data ]
>   [ perf record: Captured and wrote 1.787 MB perf.data ]
>
> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
> ---
[SNIP]
> +
> +static int perf_kwork__record(struct perf_kwork *kwork,
> +                             int argc, const char **argv)
> +{
> +       const char **rec_argv;
> +       unsigned int rec_argc, i, j;
> +       struct kwork_class *class;
> +
> +       const char *const record_args[] = {
> +               "record",
> +               "-a",
> +               "-R",
> +               "-m", "1024",
> +               "-c", "1",

Please consider adding '--synth task' to skip costly synthesis
if you don't need user space symbols.

> +       };
> +
> +       rec_argc = ARRAY_SIZE(record_args) + argc - 1;
> +
> +       list_for_each_entry(class, &kwork->class_list, list)
> +               rec_argc += 2 * class->nr_tracepoints;
> +
> +       rec_argv = calloc(rec_argc + 1, sizeof(char *));
> +       if (rec_argv == NULL)
> +               return -ENOMEM;
> +
> +       for (i = 0; i < ARRAY_SIZE(record_args); i++)
> +               rec_argv[i] = strdup(record_args[i]);
> +
> +       list_for_each_entry(class, &kwork->class_list, list) {
> +               for (j = 0; j < class->nr_tracepoints; j++) {
> +                       rec_argv[i++] = strdup("-e");
> +                       rec_argv[i++] = strdup(class->tp_handlers[j].name);
> +               }
> +       }
> +
> +       for (j = 1; j < (unsigned int)argc; j++, i++)
> +               rec_argv[i] = argv[j];
> +
> +       BUG_ON(i != rec_argc);
> +
> +       pr_debug("record comm: ");
> +       for (j = 0; j < rec_argc; j++)
> +               pr_debug("%s ", rec_argv[j]);
> +       pr_debug("\n");
> +
> +       return cmd_record(i, rec_argv);
> +}