Da documentação do Kernel intitulada: Cgroup de prioridade de rede .
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net_prio.prioidx
This file is read-only, and is simply informative. It contains a unique integer value that the kernel uses as an internal representation of this cgroup.
net_prio.ifpriomap
This file contains a map of the priorities assigned to traffic originating from processes in this group and egressing the system on various interfaces. It contains a list of tuples in the form <ifname priority>. Contents of this file can be modified by echoing a string into the file using the same tuple format. for example:
echo "eth0 5" > /sys/fs/cgroups/net_prio/iscsi/net_prio.ifpriomapThis command would force any traffic originating from processes belonging to the iscsi net_prio cgroup and egressing on interface eth0 to have the priority of said traffic set to the value 5. The parent accounting group also has a writeable 'net_prio.ifpriomap' file that can be used to set a system default priority.
Eu acredito que essas prioridades funcionam onde quanto maior o número, maior a precedência. Na página tc man:
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PRIO The PRIO qdisc is a non-shaping container for a configurable
number of classes which are dequeued in order. This allows for
easy prioritization of traffic, where lower classes are
only able to send if higher ones have no packets available. To
facilitate configuration, Type Of Service bits are honored by
default.
Portanto, se houver pacotes para uma classe mais baixa, eles terão que esperar até que não haja nenhum de uma classe numerada mais alta.