On 29.12.2015 02:09, Jim Fehlig wrote:
> The libxl_device_nic structure supports specifying an outgoing rate
> limit based on a time interval and bytes allowed per interval. In xl
> config a rate limit is specified as "<RATE>/s@<INTERVAL>". INTERVAL
> is optional and defaults to 50ms.
>
> libvirt expresses outgoing limits by average (required), peak, burst,
> and floor attributes in units of KB/s. This patch supports the outgoing
> bandwidth limit by converting the average KB/s to bytes per interval
> based on the same default interval (50ms) used by xl.
>
> Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
> ---
> src/libxl/libxl_conf.c | 39 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 39 insertions(+)
>
> diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
> index 23c74e7..6320421 100644
> --- a/src/libxl/libxl_conf.c
> +++ b/src/libxl/libxl_conf.c
> @@ -1093,6 +1093,7 @@ libxlMakeNic(virDomainDefPtr def,
> {
> bool ioemu_nic = def->os.type == VIR_DOMAIN_OSTYPE_HVM;
> virDomainNetType actual_type = virDomainNetGetActualType(l_nic);
> + virNetDevBandwidthPtr actual_bw;
>
> /* TODO: Where is mtu stored?
> *
> @@ -1206,6 +1207,44 @@ libxlMakeNic(virDomainDefPtr def,
> #endif
> }
>
> + /*
> + * Set bandwidth.
> + * From $xen-sources/docs/misc/xl-network-configuration.markdown:
> + *
> + *
> + * Specifies the rate at which the outgoing traffic will be limited to.
> + * The default if this keyword is not specified is unlimited.
> + *
> + * The rate may be specified as "<RATE>/s" or optionally "<RATE>/s@<INTERVAL>".
> + *
> + * `RATE` is in bytes and can accept suffixes:
> + * GB, MB, KB, B for bytes.
> + * Gb, Mb, Kb, b for bits.
> + * `INTERVAL` is in microseconds and can accept suffixes: ms, us, s.
> + * It determines the frequency at which the vif transmission credit
> + * is replenished. The default is 50ms.
> +
> + * Vif rate limiting is credit-based. It means that for "1MB/s@20ms",
> + * the available credit will be equivalent of the traffic you would have
> + * done at "1MB/s" during 20ms. This will results in a credit of 20,000
> + * bytes replenished every 20,000 us.
> + *
> + *
> + * libvirt doesn't support the notion of rate limiting over an interval.
> + * Similar to xl's behavior when interval is not specified, set a default
> + * interval of 50ms and calculate the number of bytes per interval based
> + * on the specified average bandwidth.
> + */
> + actual_bw = virDomainNetGetActualBandwidth(l_nic);
> + if (actual_bw && actual_bw->out && actual_bw->out->average) {
> + uint64_t bytes_per_sec = actual_bw->out->average * 1024;
> + uint64_t bytes_per_interval =
> + (((uint64_t) bytes_per_sec * 50000UL) / 1000000UL);
> +
> + x_nic->rate_bytes_per_interval = bytes_per_interval;
> + x_nic->rate_interval_usecs = 50000UL;
> + }
> +
Interesting. I'd expect:
x_nic->rate_bytes_per_interval = bytes_per_sec;
x_nic->rate_interval_usecs = 1000*1000;
I mean, if I understood the xl way of rate limiting correctly, one says
how much bytes can be sent for how long. so for 1MB/s I'd expect to send
1024*1024 bytes each second.
Or am I missing something?
Michal
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