[Libguestfs] [PATCH nbdkit 1/3] filters: stats: Show size in GiB, rate in MiB/s

[Richard W.M. Jones]

On Sat, Nov 30, 2019 at 02:17:05AM +0200, Nir Soffer wrote:
> I find bytes and bits-per-second unhelpful and hard to parse. Using GiB
> for sizes works for common disk images, and MiB/s works for common
> storage throughput.
> 
> Here is an example run with this change:
> 
> $ ./nbdkit --foreground \
>     --unix /tmp/nbd.sock \
>     --exportname '' \
>     --filter stats \
>     file file=/var/tmp/dst.img \
>     statsfile=/dev/stderr \
>     --run 'qemu-img convert -p -n -f raw -O raw -T none /var/tmp/fedora-30.img nbd:unix:/tmp/nbd.sock'
>     (100.00/100%)
> elapsed time: 2.313 s
> write: 1271 ops, 1.14 GiB, 502.63 MiB/s
> zero: 1027 ops, 4.86 GiB, 2153.24 MiB/s
> extents: 1 ops, 2.00 GiB, 885.29 MiB/s
> ---
>  filters/stats/stats.c | 34 +++++++++++++++++++---------------
>  1 file changed, 19 insertions(+), 15 deletions(-)
> 
> diff --git a/filters/stats/stats.c b/filters/stats/stats.c
> index 98282e2..45bedae 100644
> --- a/filters/stats/stats.c
> +++ b/filters/stats/stats.c
> @@ -49,6 +49,10 @@
>  #include "cleanup.h"
>  #include "tvdiff.h"
>  
> +#define MiB 1048576.0
> +#define GiB 1073741824.0
> +#define USEC 1000000.0
> +
>  static char *filename;
>  static bool append;
>  static FILE *fp;
> @@ -64,34 +68,34 @@ static uint64_t extents_ops, extents_bytes;
>  static uint64_t cache_ops, cache_bytes;
>  
>  static inline double
> -calc_bps (uint64_t bytes, int64_t usecs)
> +calc_mibps (uint64_t bytes, int64_t usecs)
>  {
> -  return 8.0 * bytes / usecs * 1000000.;
> +  return bytes / MiB / usecs * USEC;
>  }

The idea isn't bad, but I think we can lose data doing this.  What
happens if the rate is substantially less than 1 megabit?

We either ought to scale this according to the size of the number
being printed, or else let the user select it.  For scaling, here's
some code from fio:

https://github.com/axboe/fio/blob/bef74db41fb5a1607fd55cb86544165fc08acac1/lib/num2str.c#L72

Rich.

-- 
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