Re: [libvirt] [PATCH 2/2] libxl: support vif outgoing bandwidth QoS

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(a)suse.com&gt; > --- > 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?