Re: [Gems-users] question about link utilization

[Niket Agarwal <niketa@xxxxxxxxxxxxx>]

If you have a look at printStats in Switch.C, the utilization 
percentages are for the throttles which are essentially outlinks.
Zhang Yu wrote:
> 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 
> <mailto: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
> >     <mailto: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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