Re: [libvirt] [PATCH 1/4] networkAllocateActualDevice: Set QoS for bridgeless networks too

https://bugzilla.redhat.com/show_bug.cgi?id=1055484 Currently, libvirt's XML schema of network allows QoS to be defined for every network even though it has no bridge. For instance: <network> <name>vdsm-no-bridge</name> <forward mode='passthrough'> <interface dev='em1.10'/> </forward> <bandwidth> <inbound average='1000' peak='5000' burst='1024'/> <outbound average='1000' burst='1024'/> </bandwidth> </network> The bandwidth limitations can be, however, applied even on such networks. In fact, they are gonna be applied on the interface that will

be connected to the network on a domain startup. This approach, however, has one limitation. With bridged networks, there are two points where QoS can be set: bridge and domain interface. The lower limit of the two is enforced then. For instance, if the interface has 10Mbps average, but the network only 1Mbps, there's no way for interface to transmit packets faster than the 1Mbps limit. With two points this is enforced by kernel. With only one point, we must combine both QoS settings into one which is set afterwards. Look at virNetDevBandwidthMinimal() and you'll understand immediately what I mean. Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/libvirt_private.syms | 1 + src/network/bridge_driver.c | 25 +++++++++++- src/util/virnetdevbandwidth.c | 88 +++++++++++++++++++++++++++++++++++++++++++ src/util/virnetdevbandwidth.h | 6 +++ 4 files changed, 118 insertions(+), 2 deletions(-)

- if (bandwidth && virNetDevBandwidthCopy(&iface->data.network.actual->bandwidth, - bandwidth) < 0) + /* For a bridgeless networks we must take into account any QoS set to them.

+ +static void +virNetDevBandwidthRateMinimal(virNetDevBandwidthRatePtr result, + virNetDevBandwidthRatePtr band1, + virNetDevBandwidthRatePtr band2) +{ + if (!band1 || !band2) { + memcpy(result, band1 ? band1 : band2, sizeof(*result));

+ return; + } + + /* We can't do a simple MIN() here, because zero value doesn't mean the + * narrowest limit, but and unset value. Hence we need symmetric F(a, b)

+ * so that: + * F(a, 0) = F(0, a) = a; special corner case: F(0, 0) = 0 + * F(a, b) = MIN(a, b) for a != 0 and b != 0 + */ +#define NON_ZERO_MIN(a, b) \ + ((a) && (b) ? MIN(a, b) : (a) ? (a) : (b))

+virNetDevBandwidthMinimal(virNetDevBandwidthPtr *result, + virNetDevBandwidthPtr band1, + virNetDevBandwidthPtr band2) +{ + int ret = -1; + + if (!band1 && !band2) { + /* Nothing to compute */ + *result = NULL; + return 0; + }

+ + if (!band1->in && !band2->in) { + /* nada */ + } else {

+ if (VIR_ALLOC((*result)->in) < 0) + goto cleanup; + + virNetDevBandwidthRateMinimal((*result)->in, band1->in, band2->in); + } + + if (!band1->out && !band2->out) { + /* nada */ + } else {