linux-kernel - Re: [PATCH v3 3/3] tracing: format non-nanosec times from tsc clock without a decimal point.

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Date:	Mon, 24 Sep 2012 23:27:15 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	David Sharp <dhsharp@...gle.com>
Cc:	linux-kernel@...r.kernel.org,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [PATCH v3 3/3] tracing: format non-nanosec times from tsc clock
 without a decimal point.

On Thu, 2012-09-20 at 15:52 -0700, David Sharp wrote:
> With the addition of the "tsc" clock, formatting timestamps to look like
> fractional seconds is misleading. Mark clocks as either in nanoseconds or
> not, and format non-nanosecond timestamps as decimal integers.

I got this:

/work/autotest/nobackup/linux-test.git/kernel/trace/trace_output.c:636: undefined reference to `__umoddi3'
/work/autotest/nobackup/linux-test.git/kernel/trace/trace_output.c:636: undefined reference to `__udivdi3'
/work/autotest/nobackup/linux-test.git/kernel/trace/trace_output.c:636: undefined reference to `__umoddi3'
/work/autotest/nobackup/linux-test.git/kernel/trace/trace_output.c:636: undefined reference to `__umoddi3'
/work/autotest/nobackup/linux-test.git/kernel/trace/trace_output.c:636: undefined reference to `__udivdi3'
/work/autotest/nobackup/linux-test.git/kernel/trace/trace_output.c:636: undefined reference to `__umoddi3'
/work/autotest/nobackup/linux-test.git/kernel/trace/trace_output.c:636: undefined reference to `__udivdi3'

when building for x86_32.

> +	int ret;
> +	struct trace_seq *s = &iter->seq;
> +	unsigned long verbose = trace_flags & TRACE_ITER_VERBOSE;
> +	unsigned long in_ns = iter->iter_flags & TRACE_FILE_TIME_IN_NS;
> +	unsigned long long abs_ts = iter->ts - iter->tr->time_start;
> +	unsigned long long rel_ts = next_ts - iter->ts;
> +	unsigned long mark_thresh;
> +
> +	if (in_ns) {
> +		abs_ts = ns2usecs(abs_ts);
> +		rel_ts = ns2usecs(rel_ts);
> +		mark_thresh = preempt_mark_thresh_us;
> +	} else
> +		mark_thresh = preempt_mark_thresh_cycles;
> +
> +	if (verbose && in_ns) {
> +		ret = trace_seq_printf(
> +				s, "[%08llx] %lld.%03lldms (+%lld.%03lldms): ",
> +				ns2usecs(iter->ts),
> +				abs_ts / USEC_PER_MSEC,
> +				abs_ts % USEC_PER_MSEC,
> +				rel_ts / USEC_PER_MSEC,

You can't divide 64 bit numbers in the kernel. It breaks on 32bit archs.

-- Steve

> +				rel_ts % USEC_PER_MSEC);
> +	} else if (verbose && !in_ns) {
> +		ret = trace_seq_printf(
> +				s, "[%016llx] %lld (+%lld): ",
> +				iter->ts, abs_ts, rel_ts);
> +	} else { /* !verbose */
> +		ret = trace_seq_printf(
> +				s, " %4lld%s%c: ",
> +				abs_ts,
> +				in_ns ? "us" : "",
> +				rel_ts > mark_thresh ? '!' :
> +				  rel_ts > 1 ? '+' : ' ');
> +	}
> +	return ret;
>  }
>  
>  int trace_print_context(struct trace_iterator *iter)
>  {
>  	struct trace_seq *s = &iter->seq;
>  	struct trace_entry *entry = iter->ent;
> -	unsigned long long t = ns2usecs(iter->ts);
> -	unsigned long usec_rem = do_div(t, USEC_PER_SEC);
> -	unsigned long secs = (unsigned long)t;
> +	unsigned long long t;
> +	unsigned long secs, usec_rem;
>  	char comm[TASK_COMM_LEN];
>  	int ret;
>  
> @@ -644,8 +677,13 @@ int trace_print_context(struct trace_iterator *iter)
>  			return 0;
>  	}
>  
> -	return trace_seq_printf(s, " %5lu.%06lu: ",
> -				secs, usec_rem);
> +	if (iter->iter_flags & TRACE_FILE_TIME_IN_NS) {
> +		t = ns2usecs(iter->ts);
> +		usec_rem = do_div(t, USEC_PER_SEC);
> +		secs = (unsigned long)t;
> +		return trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
> +	} else
> +		return trace_seq_printf(s, "%12llu: ", iter->ts);
>  }
>  
>  int trace_print_lat_context(struct trace_iterator *iter)
> @@ -659,36 +697,30 @@ int trace_print_lat_context(struct trace_iterator *iter)
>  			   *next_entry = trace_find_next_entry(iter, NULL,
>  							       &next_ts);
>  	unsigned long verbose = (trace_flags & TRACE_ITER_VERBOSE);
> -	unsigned long abs_usecs = ns2usecs(iter->ts - iter->tr->time_start);
> -	unsigned long rel_usecs;
> +
>  
>  	/* Restore the original ent_size */
>  	iter->ent_size = ent_size;
>  
>  	if (!next_entry)
>  		next_ts = iter->ts;
> -	rel_usecs = ns2usecs(next_ts - iter->ts);
>  
>  	if (verbose) {
>  		char comm[TASK_COMM_LEN];
>  
>  		trace_find_cmdline(entry->pid, comm);
>  
> -		ret = trace_seq_printf(s, "%16s %5d %3d %d %08x %08lx [%08llx]"
> -				       " %ld.%03ldms (+%ld.%03ldms): ", comm,
> -				       entry->pid, iter->cpu, entry->flags,
> -				       entry->preempt_count, iter->idx,
> -				       ns2usecs(iter->ts),
> -				       abs_usecs / USEC_PER_MSEC,
> -				       abs_usecs % USEC_PER_MSEC,
> -				       rel_usecs / USEC_PER_MSEC,
> -				       rel_usecs % USEC_PER_MSEC);
> +		ret = trace_seq_printf(
> +				s, "%16s %5d %3d %d %08x %08lx ",
> +				comm, entry->pid, iter->cpu, entry->flags,
> +				entry->preempt_count, iter->idx);
>  	} else {
>  		ret = lat_print_generic(s, entry, iter->cpu);
> -		if (ret)
> -			ret = lat_print_timestamp(s, abs_usecs, rel_usecs);
>  	}
>  
> +	if (ret)
> +		ret = lat_print_timestamp(iter, next_ts);
> +
>  	return ret;
>  }
>  


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