Re: problem with the "write_bw_log" parameter in a virtualized environment using a write iopattern

[Ivan Frain <ivan.frain@seanodes.com>]

Jens Axboe a écrit :
> On Fri, Jul 31 2009, Ivan Frain wrote:
>
>> Hi everybody,
>>
>> I'am using fio in a vmware virtualized environment. I have got a guest
>> virtual machine based on centos5.2 on which I run fio in order to
>> measure the virtual disks IO performances.
>> I use the "write_bw_log" parameter in order to build graphs for the
>> experiments but the problem is that the file generated by fio for each
>> job is empty (size = 0).
>> However, i also use "write_clat_log" parameter and the 'clat.log' and
>> 'slat.log' files are not empty. The mean bandwidth in the fio output
>> summary seams to be good.
>>
>
> I wonder how long that bug has been there... It's due to a botched
> memcpy in the fio core. There are two stat sample times, yet it
> overwrites only the first one (being 0, or DDIR_READ, which explains why
> the read one works).
>
> Try the below patch, it's also committed now.
>
> diff --git a/fio.c b/fio.c
> index ba9e384..7ad1b57 100644
> --- a/fio.c
> +++ b/fio.c
> @@ -1105,7 +1105,10 @@ static void *thread_main(void *data)
>  	clear_state = 0;
>  	while (keep_running(td)) {
>  		fio_gettime(&td->start, NULL);
> -		memcpy(&td->ts.stat_sample_time, &td->start, sizeof(td->start));
> +		memcpy(&td->ts.stat_sample_time[0], &td->start,
> +				sizeof(td->start));
> +		memcpy(&td->ts.stat_sample_time[1], &td->start,
> +				sizeof(td->start));
>  		memcpy(&td->tv_cache, &td->start, sizeof(td->start));
>
>  		if (td->o.ratemin[0] || td->o.ratemin[1])
>
>

Well, this patch works very well, the bw log file is filled again.
Thank you for your quick answer.

FIO rocks !!

Best regards,

Ivan Frain

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