[j-nsp] QFX5100 buffer allocation

[Michael Still]

If you don't need the lossless queue then you can axe most of it. This
is what I've done:
set class-of-service shared-buffer ingress percent 100
set class-of-service shared-buffer ingress buffer-partition lossless percent 5
set class-of-service shared-buffer ingress buffer-partition lossy percent 95
set class-of-service shared-buffer ingress buffer-partition
lossless-headroom percent 0
set class-of-service shared-buffer egress percent 100
set class-of-service shared-buffer egress buffer-partition lossless percent 5
set class-of-service shared-buffer egress buffer-partition lossy percent 90
set class-of-service shared-buffer egress buffer-partition multicast percent 5

> show class-of-service shared-buffer
Ingress:
  Total Buffer     :  12480.00 KB
  Dedicated Buffer :  2912.81 KB
  Shared Buffer    :  9567.19 KB
    Lossless          :  478.36 KB
    Lossless Headroom :  0.00 KB
    Lossy             :  9088.83 KB

  Lossless Headroom Utilization:
  Node Device         Total          Used                  Free
  0                   0.00 KB        0.00 KB               0.00 KB

Egress:
  Total Buffer     :  12480.00 KB
  Dedicated Buffer :  3744.00 KB
  Shared Buffer    :  8736.00 KB
    Lossless          :  436.80 KB
    Multicast         :  436.80 KB
    Lossy             :  7862.40 KB

You may be able to tweak even further for your own needs.



On Wed, May 16, 2018 at 12:06 PM, Brian Rak <brak at gameservers.com> wrote:
> We've been trying to track down why our 5100's are dropping traffic due to
> lack of buffer space, even with very low link utilization.
>
> It seems like they're classifying all our traffic as best-effort:
>> show interfaces xe-0/0/49:0 extensive
> ....
>     Carrier transitions: 1, Errors: 0, Drops: 276796488, Collisions: 0, Aged
> packets: 0, FIFO errors: 0, HS link CRC errors: 0, MTU errors: 0, Resource
> errors: 0, Bucket drops: 0
>   Egress queues: 12 supported, 5 in use
>   Queue counters:       Queued packets  Transmitted packets Dropped packets
>     0                                0 1876090180637            276796488
>     3                                0 0                    0
>     4                                0 0                    0
>     7                                0 663877                    0
>     8                                0 0                    0
>
> Then, if we look at those queues:
>
>> show class-of-service forwarding-class
> Forwarding class                       ID      Queue  Policing priority
> No-Loss
>   best-effort                          0         0 normal        Disabled
>   fcoe                                 1         3 normal        Enabled
>   no-loss                              2         4 normal        Enabled
>   network-control                      3         7 normal        Disabled
>   mcast                                8         8 normal        Disabled
>
> So whatever, we've got queues configured for traffic we never see. That's
> not really a huge deal.  But then:
>
>> show class-of-service shared-buffer egress
> Egress:
>   Total Buffer     :  12480.00 KB
>   Dedicated Buffer :  3744.00 KB
>   Shared Buffer    :  8736.00 KB
>     Lossless          :  4368.00 KB
>     Multicast         :  1659.84 KB
>     Lossy             :  2708.16 KB
>
> To me, this appears that the 5100's by default reserve about 70% of the
> available shared port buffers for lossless+multicast traffic. The
> documentation seems to back me up here:
>
> https://www.juniper.net/documentation/en_US/junos/topics/concept/cos-qfx-series-buffer-configuration-understanding.html#jd0e1441
> https://www.juniper.net/documentation/en_US/junos/topics/example/cos-shared-buffer-allocation-lossy-ucast-qfx-series-configuring.html
>
> Has anyone else encountered this?  We're going to be adjusting the buffers
> per the documentation, but I'd be really interested to hear if anyone has
> hit this before.
>
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp



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