Hola! rikudu

Respondiendo a tu pregunta:
¿O hay otra forma de recolectar el consumo en tiempo real de una conexión pppoe sin causar un alto uso de la CPU en ne20?
Si es possible con el comando "display access-user user-id XXXX verbose "

Esto es lo que despliega el commando, si no quieres incrementar el CPU del equipo seria conveniente revisar unicamente el performance de 1 usuario, o conjuntos de 100 para snmp,esto dependiendo de que tanto incremente el CPU.

Nota: Este comando fue tomado de un NE20E-S2 V800R010C00 puede diferir un poco de tu version y modelo de equipo.

<Huawei> display access-user user-id 32768 verbose
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Basic:
User access index : 32768
State : Used
User name : 2333(Radius)
Domain name : huawei
User backup state : No
RUI user state : -
User access interface : GigabitEthernet3/0/2
User access PeVlan/CeVlan : -/-
User access slot : 3
User MAC : 6000-03e3-951b
User IP address : 192.169.112.253
User IP netmask : 255.255.255.255
User gateway address : 192.169.112.1
User Authen IP Type : ipv4/-/-
User Basic IP Type : -/-/-
Server IP : 192.169.112.1
IPv6 address assignment mode : -
User lease : 2017-08-08 13:40---2017-08-08 13:40
Remain lease(sec) : 245026
User access type : IPOE
User authentication type : Bind authentication
Agent-Circuit-Id : -
Agent-Remote-Id : -
Access-line-id Information(dhcpv4 option82) : -
Access start time : 2017-08-08 13:40
User-Group : -
Next-hop : -
Policy-route-IPV6-address : -

AAA:
RADIUS-server-template : huawei
Server-template of second acct : -
Current authen method : RADIUS authentication
Authen result : Success
Current author method : Idle
Author result : Success
Action flag : Idle
Authen state : Authed
Author state : Idle
Configured accounting method : No accounting
Quota-out : Offline
Current accounting method : No accounting
Realtime-accounting-switch : Close
Realtime-accounting-interval(sec) : -
Realtime-accounting-send-update : No
Realtime-accounting-traffic-update : No
Accounting start time : 2017-08-08 13:40
Online time (h:min:sec) : 01:25:04
Accounting state : Ready
MTU : 1500
Idle-cut direction : Both
Idle-cut-data (time,rate,idle) : 0 sec, 60 kbyte/min, 0 min 0 sec
Ipv4 Realtime speed : 0 kbyte/min
Ipv4 Realtime speed inbound : 0 kbyte/min
Ipv4 Realtime speed outbound : 0 kbyte/min
Redirect Weburl : http://8.33.71.91

Dot1X:
User MSIDSN name : -
EAP user : No
MD5 end : No

VPN&Policy-route:
Vpn-Instance : -
Vpn-Instance(inbound) : -

Multicast Service:
Multicast-profile : -
Multicast-profile-ipv6 : -
Max Multicast List Number : 4
IGMP enable : Yes

ACL&QoS:
Link bandwidth auto adapt : Disable
UpPriority : Unchangeable
DownPriority : Unchangeable
FQ:
fq=be;shaping.value=80000 pbs=15000;sch=wfq weight=10;dir=in
fq=cs6;shaping.percentage=80;dir=in(Radius)
fq=be;shaping.value=80000 pbs=15000;sch=wfq weight=10;dir=out
fq=cs6;shaping.percentage=80;dir=out(Radius)

Active EDSG services by order:
Service0 info : b
Service1 info : c
Service2 info : d
Service3 info : e

Flow Statistic:
contain l2-head : Yes
Flow-Statistic-Up : Yes
Flow-Statistic-Down : Yes
Up packets number(high,low) : (0,0)
Up bytes number(high,low) : (0,0)
Down packets number(high,low) : (0,0)
Down bytes number(high,low) : (0,0)
IPV6 Up packets number(high,low) : (0,0)
IPV6 Up bytes number(high,low) : (0,0)
IPV6 Down packets number(high,low) : (0,0)
IPV6 Down bytes number(high,low) : (0,0)
Value-added-service Flow Statistic :
EDSG(service0) Up packets number(high,low) : (0,0)
EDSG(service0) Up bytes number(high,low) : (0,0)
EDSG(service0) Down packets number(high,low) : (0,0)
EDSG(service0) Down bytes number(high,low) : (0,0)
Dropped-cs7 : 0,200;20;0,300;30
Dropped-cs6 : 0,200;20;0,300;30
Dropped-ef : 0,200;20;0,300;30
Dropped-af4 : 0,200;20;0,300;30
Dropped-af3 : 0,200;20;0,300;30
Dropped-af2 : 0,200;20;0,300;30
Dropped-af1 : 0,200;20;0,300;30
Dropped-be : 0,200;20;0,300;30
Remote Dropped-cs7 : 0,200;20;0,300;30
Remote Dropped-cs6 : 0,200;20;0,300;30
Remote Dropped-ef : 0,200;20;0,300;30
Remote Dropped-af4 : 0,200;20;0,300;30
Remote Dropped-af3 : 0,200;20;0,300;30
Remote Dropped-af2 : 0,200;20;0,300;30
Remote Dropped-af1 : 0,200;20;0,300;30
Remote Dropped-be : 0,200;20;0,300;30

Dslam information :
Circuit ID :-
Remote ID :-
Actual datarate upstream :0(Kbps)
Actual datarate downstream :0(Kbps)
Min datarate upstream :0(Kbps)
Min datarate downstream :0(Kbps)
Attainable datarate upstream :0(Kbps)
Attainable datarate downstream :0(Kbps)
Max datarate upstream :0(Kbps)
Max datarate downstream :0(Kbps)
Min lowpower datarate upstream :0(Kbps)
Min lowpower datarate downstream :0(Kbps)
Max delay upstream :0(s)
Max delay downstream :0(s)
Actual delay upstream :0(s)
Actual delay downstream :0(s)
Access loop encapsulation :0x000000
-------------------------------------------------------------------

Para mas informacion revisar la documentacion del equipo.