[libvirt] [PATCH 2/2] libxl: support vif outgoing bandwidth QoS
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>
---
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;
+ }
+
return 0;
}
--
2.1.4