Re: [Libguestfs] [PATCH nbdkit 1/3] filters: stats: Show size in GiB, rate in MiB/s
On Sat, Nov 30, 2019 at 8:58 AM Richard W.M. Jones <rjones(a)redhat.com> wrote:
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?
Do you mean values less than 0.01 GiB, or 0.01 MiB/s? This does not
look like interesting use case to me. We can use .3f format to avoid
losing data in such cases.
We either ought to scale this according to the size of the number
being printed, or else let the user select it.
It is better to scale the unit based on the size, using the same
way ls -lh does it, but I don't have time to work on this now.
For scaling, here's
some code from fio:
https://github.com/axboe/fio/blob/bef74db41fb5a1607fd55cb86544165fc08acac...
Rich.
--
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