linux-kernel - Re: [PATCH 1/2] perf tools: add 'perf irq' to measure the hardware interrupts

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Date:   Tue, 12 Jan 2021 22:50:57 +0300
From:   Alexei Budankov <abudankov@...wei.com>
To:     Bixuan Cui <cuibixuan@...wei.com>, <peterz@...radead.org>,
        <mingo@...hat.com>, <acme@...nel.org>, <mark.rutland@....com>,
        <alexander.shishkin@...ux.intel.com>, <jolsa@...hat.com>,
        <namhyung@...nel.org>, <linux-kernel@...r.kernel.org>
CC:     <john.wanghui@...wei.com>, <abudankov@...wei.com>
Subject: Re: [PATCH 1/2] perf tools: add 'perf irq' to measure the hardware
 interrupts


Hi Bixuan,

On 12.01.2021 15:55, Bixuan Cui wrote:
> Add 'perf irq' to trace/measure the hardware interrupts.
> 
> Now three functions are provided:
>   1. 'perf irq record <command>' to record the irq handler events.
>   2. 'perf irq script' to see a detailed trace of the workload that
>    was recorded.
>   3. 'perf irq timeconsume' to calculate the time consumed by each
>    hardware interrupt processing function.
> 
> Signed-off-by: Bixuan Cui <cuibixuan@...wei.com>

Thanks for the patches. There is still something that could be improved.

> ---
>  tools/perf/Build         |   1 +
>  tools/perf/builtin-irq.c | 288 +++++++++++++++++++++++++++++++++++++++
>  tools/perf/builtin.h     |   1 +
>  tools/perf/perf.c        |   1 +
>  4 files changed, 291 insertions(+)
>  create mode 100644 tools/perf/builtin-irq.c
> 

<SNIP>

> +
> +static int __cmd_record(int argc, const char **argv)
> +{
> +	unsigned int rec_argc, i, j;
> +	const char **rec_argv;
> +	const char * const record_args[] = {
> +		"record",
> +		"-a",

I see it works also like this:

sudo perf record -p PID -c 1 -e irq:irq_handler_entry,irq:irq_handler_exit
sudo perf record -R -c 1 -e irq:irq_handler_entry,irq:irq_handler_exit -- find /

This -a option jointly with -p option could be made configurable from
the command line for perf irq mode.

> +		"-R",
> +		"-m", "1024",

Do you see data losses with default buffer size of 512KB
when capturing trace in your specific use case?

If not then this -m could be avoided or made configurable
if you still need it.

Regards,
Alexei