linux-kernel - Re: [PATCH] taskstats: Add e/u/stime for TGID command

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Message-ID: <58BE08E4.5030603@windriver.com>
Date:   Tue, 7 Mar 2017 09:12:04 +0800
From:   ZhangXiao <xiao.zhang@...driver.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     xiao.zhang@...driver.com, bsingharora@...il.com,
        linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH] taskstats: Add e/u/stime for TGID command



在 2017年03月07日 06:40, Andrew Morton 写道:
> On Fri, 3 Mar 2017 10:33:44 +0800 Zhang Xiao <xiao.zhang@...driver.com> wrote:
> 
>> Add elapsed time, user CPU time and system CPU time to
>> thread group status request.
>>
>> --- a/kernel/taskstats.c
>> +++ b/kernel/taskstats.c
>> @@ -210,6 +210,7 @@ static int fill_stats_for_tgid(pid_t tgid, struct taskstats *stats)
>>  	struct task_struct *tsk, *first;
>>  	unsigned long flags;
>>  	int rc = -ESRCH;
>> +	u64 delta, utime, stime;
>>  
>>  	/*
>>  	 * Add additional stats from live tasks except zombie thread group
>> @@ -238,6 +239,16 @@ static int fill_stats_for_tgid(pid_t tgid, struct taskstats *stats)
>>  		 */
>>  		delayacct_add_tsk(stats, tsk);
>>  
>> +		/* calculate task elapsed time in nsec */
>> +		delta = ktime_get_ns() - tsk->start_time;
>> +		/* Convert to micro seconds */
>> +		do_div(delta, NSEC_PER_USEC);
>> +		stats->ac_etime += delta;
>> +
>> +		task_cputime(tsk, &utime, &stime);
>> +		stats->ac_utime += div_u64(utime, NSEC_PER_USEC);
>> +		stats->ac_stime += div_u64(stime, NSEC_PER_USEC);
>> +
>>  		stats->nvcsw += tsk->nvcsw;
>>  		stats->nivcsw += tsk->nivcsw;
>>  	} while_each_thread(first, tsk);
> 
> hm, OK, we were just leaving these at zero.  Seems sane to me.
> 
> It would be more efficient and perhaps more deterministic to sample
> ktime just once?
> 

yes, that makes the code more readable. :-)

Thanks
Xiao

> --- a/kernel/taskstats.c~taskstats-add-e-u-stime-for-tgid-command-fix
> +++ a/kernel/taskstats.c
> @@ -211,6 +211,7 @@ static int fill_stats_for_tgid(pid_t tgi
>  	unsigned long flags;
>  	int rc = -ESRCH;
>  	u64 delta, utime, stime;
> +	u64 start_time;
>  
>  	/*
>  	 * Add additional stats from live tasks except zombie thread group
> @@ -228,6 +229,7 @@ static int fill_stats_for_tgid(pid_t tgi
>  		memset(stats, 0, sizeof(*stats));
>  
>  	tsk = first;
> +	start_time = ktime_get_ns();
>  	do {
>  		if (tsk->exit_state)
>  			continue;
> @@ -240,7 +242,7 @@ static int fill_stats_for_tgid(pid_t tgi
>  		delayacct_add_tsk(stats, tsk);
>  
>  		/* calculate task elapsed time in nsec */
> -		delta = ktime_get_ns() - tsk->start_time;
> +		delta = start_time - tsk->start_time;
>  		/* Convert to micro seconds */
>  		do_div(delta, NSEC_PER_USEC);
>  		stats->ac_etime += delta;
> _
> 
>