Re: [Gems-users] question about link utilization

["Zhang Yu" <thuzhangyu@xxxxxxxxx>]

Then for the stats below:

switch_16_inlinks: 16
switch_16_outlinks: 16
links_utilized_percent_switch_16: 8.8189e-07
  links_utilized_percent_switch_16_link_0: 7.39941e-06 bw: 1215752192 base_latency: 1
  links_utilized_percent_switch_16_link_1: 2.43733e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_2: 1.6149e-06 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_3: 2.37152e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_4: 2.67335e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_5: 3.68777e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_6: 2.3806e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_7: 5.06984e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_8: 2.603e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_9: 2.30344e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_10: 6.80366e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_11: 2.35791e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_12: 1.04529e-06 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_13: 2.49407e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_14: 2.34429e-07 bw: 1410065408 base_latency: 6
  links_utilized_percent_switch_16_link_15: 2.97972e-07 bw: 1410065408 base_latency: 6

switch16 has 16 outlinks and 16 inlinks, so that's 32 links in total, while the network stats only provide the utilization of 16 links of this switch. In this case, what should these 16 links be, outgoing links?

Thanks,
Yu

On Jan 31, 2008 10:20 PM, Greg Byrd <gbyrd@xxxxxxxx> wrote:

They're not really bidirectional links.  There are two physical links, one in each direction.  The utilization for one direction is completely independent of the utilization in the other direction.

...Greg


Zhang Yu wrote:

Thanks for the reply. I don't understand the meaning of the link utilization in the stats. Should it be the average utilization of both incoming link and outgoing link? For example, if switch0_link7 is connected to switch2_link 4, and both of the links are bidirectional(which means switch0_link7(or switch2_link4) is composed of 2 links, one is incoming and the other is outgoing). If this is the case, then the two links of the two switches should have the same utilization.

Thanks,
Yu

On Jan 31, 2008 10:01 PM, Niket Agarwal <niketa@xxxxxxxxxxxxx> wrote:

Two switches connected to each other will have two different "physical"
links in opposite directions.

But why should the link utilizations be the same ? The traffic that is
going in either direction has to be exactly the same for this.

 - Niket

Zhang Yu wrote:
> Hi,
>
> I'm wondering how the intra-chip switches connect to each other. As I
> understand that, when the 2 intra-chip switches are connect, they

> share wo links (different direction). In this case, the certain

> connected links for these two switches should have the same link
> utilization. However, when I check with the statistics, I could not
> find different links with same utilization. Do I misunderstand the
> connection between the switches? Can somebody explain this?
>
> Thanks,
> Yu

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