linux-kernel - Re: [PATCH] cpustat: print watchdog time and statistics of soft and hard interrupts in soft lockup scenes

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Date:   Wed, 21 Aug 2019 12:46:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     c00423981 <caomeng5@...wei.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpustat: print watchdog time and statistics of soft and
 hard interrupts in soft lockup scenes


A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

On Wed, Aug 21, 2019 at 04:26:17PM +0800, c00423981 wrote:
> Sorry, I cannot understand this problem accurately. I try to understand it and I guess what you want
> to express is that the return value type should be cputime64_t but not u64, just like as follows:
> 
> +static cputime64_t cpustat_curr_cputime(int cpu, int index)
> +{
> +	cputime64_t time;
> +
> +	if (index == CPUTIME_IDLE)
> +		time = get_idle_time(cpu);
> +	else if (index == CPUTIME_IOWAIT)
> +		time = get_iowait_time(cpu);
> 
> I don't know if I understand it correctly. Looking forward to your answer.

get_iowait_time(cpu) is terminally broken, see commit:

  e33a9bba85a8 ("sched/core: move IO scheduling accounting from io_schedule_timeout() into scheduler")