Re: [PATCH 09/12] trace-cmd: Convert tsc timestamps to nanosecods when reading trace data from a file

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 15 Mar 2021 08:18:29 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:

> If there is information for TSC to nanoseconds conversion in the trace
> file metadata, use it to recalculate the timestamps of all events.
> 
> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
> ---
>  lib/trace-cmd/trace-input.c | 28 ++++++++++++++++++++++++----
>  1 file changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
> index 65081007..dc9ac1d3 100644
> --- a/lib/trace-cmd/trace-input.c
> +++ b/lib/trace-cmd/trace-input.c
> @@ -1276,17 +1276,37 @@ static unsigned long long timestamp_correct(unsigned long long ts,
>  					 &host->ts_samples[mid+1]);
>  }
>  

I would add a comment saying that the below function was taken from the
Linux kernel.

-- Steve

> +static unsigned long long mul_u64_u32_shr(unsigned long long a,
> +					  unsigned long long mul, unsigned int shift)
> +{
> +	unsigned int ah, al;
> +	unsigned long long ret;
> +
> +	al = a;
> +	ah = a >> 32;
> +
> +	ret = (al * mul) >> shift;
> +	if (ah)
> +		ret += (ah * mul) << (32 - shift);
> +
> +	return ret;
> +}
> +
>  static unsigned long long timestamp_calc(unsigned long long ts,
>  					 struct tracecmd_input *handle)
>  {
> -	unsigned long long tstamp;
> +	unsigned long long t;
>  
> -	tstamp = timestamp_correct(ts, handle);
> +	t = timestamp_correct(ts, handle);
>  
>  	if (handle->ts2secs)
> -		tstamp *= handle->ts2secs;
> +		t *= handle->ts2secs;
> +	else if (handle->tsc_calc.mult) {
> +		t = mul_u64_u32_shr(t, handle->tsc_calc.mult, handle->tsc_calc.shift);
> +		t += handle->tsc_calc.offset;
> +	}
>  
> -	return tstamp;
> +	return t;
>  }
>  
>  /*