Re: [Gems-users] calculate network latency

["Lide Duan" <leaderduan@xxxxxxxxx>]

When calculating the latency between two machines, it's assumed that every switch on the path contributes 1 cycle latency in addition to the link latencies. So, in you case, the latency between L1Cache-0 and L1Cache-1 should be the link latencies (1+1+2+1+1) plus switch latencies (totally 4 switches on path), which is 10.

If you set GARNET_NETWORK to 'false', you are using simple network in which case no pipeline is simulated inside switches.

On Thu, May 29, 2008 at 4:23 AM, <xuh@xxxxxx> wrote:

Thanks for your reply!
But in my case, both GARNET_NETWORK and g_DETAIL_NETWORK are set 'false'.
And I am just using the topology from
/ruby/network/simple/Network_Files/NUCA_Mesh...

Is Garnet model still working in this case ? Btw, how do garnet model
related and the topology file work together?

Best regards,
Xu


> Hi Xu han,
>
> You must have been using Garnet network model, which simulates a more
> realistic network model. In Garnet fixed router pipeline model
> They assume the router latency itself is 4-cycle. That adds up to 10
> cycles. You might want to look into the details of Garnet network
> model in the following URL:
> http://www.cs.wisc.edu/gems/doc/gems-wiki/moin.cgi/Garnet
>
> Hope that helps,
>
> Guoqiang Yang
>
> ==========================
> Hello, gentlemen,
>
> May I ask a question about network latency in ruby:
>
> when I use a topolody specified in file
> 'NUCA_Mesh_Procs-4_ProcsPerChip-4_L2Banks-4_Memories-4.txt', whose content
> is:
> processors:4
> procs_per_chip:4
> L2banks:4
> memories:4
> bw_unit:1000
>
> ext_node:L1Cache:0 int_node:8 link_latency:1 bw_multiplier:32
> ext_node:L1Cache:1 int_node:9 link_latency:1 bw_multiplier:32
> ext_node:L1Cache:2 int_node:10 link_latency:1 bw_multiplier:32
> ext_node:L1Cache:3 int_node:11 link_latency:1 bw_multiplier:32
>
> ext_node:L2Cache:0 int_node:4 link_latency:20 bw_multiplier:32
> ext_node:L2Cache:1 int_node:5 link_latency:20 bw_multiplier:32
> ext_node:L2Cache:2 int_node:6 link_latency:20 bw_multiplier:32
> ext_node:L2Cache:3 int_node:7 link_latency:20 bw_multiplier:32
> ext_node:Directory:0 int_node:4 link_latency:100 bw_multiplier:16
> ext_node:Directory:1 int_node:5 link_latency:100 bw_multiplier:16
> ext_node:Directory:2 int_node:6 link_latency:100 bw_multiplier:16
> ext_node:Directory:3 int_node:7 link_latency:100 bw_multiplier:16
>
> int_node:0 int_node:1 link_latency:2 bw_multiplier:16
> int_node:1 int_node:3 link_latency:2 bw_multiplier:16
> int_node:2 int_node:0 link_latency:2 bw_multiplier:16
> int_node:3 int_node:2 link_latency:2 bw_multiplier:16
>
> int_node:4 int_node:8 link_latency:1 bw_multiplier:32
> int_node:5 int_node:9 link_latency:1 bw_multiplier:32
> int_node:6 int_node:10 link_latency:1 bw_multiplier:32
> int_node:7 int_node:11 link_latency:1 bw_multiplier:32
>
> int_node:8 int_node:0 link_latency:1 bw_multiplier:32
> int_node:9 int_node:1 link_latency:1 bw_multiplier:32
> int_node:10 int_node:2 link_latency:1 bw_multiplier:32
> int_node:11 int_node:3 link_latency:1 bw_multiplier:32
>
>
> THEN, in the result of topology print:
> L1Cache-0 Network Latencies
>   L1Cache-0 -> L2Cache-0 net_lat: 24
>   L1Cache-0 -> L2Cache-1 net_lat: 31
>   L1Cache-0 -> L2Cache-2 net_lat: 31
>   L1Cache-0 -> L2Cache-3 net_lat: 34
>   L1Cache-0 -> L1Cache-1 net_lat: 10
>   L1Cache-0 -> L1Cache-2 net_lat: 10
>   L1Cache-0 -> L1Cache-3 net_lat: 13
>   L1Cache-0 -> Directory-0 net_lat: 104
>   L1Cache-0 -> Directory-1 net_lat: 111
>   L1Cache-0 -> Directory-2 net_lat: 111
>   L1Cache-0 -> Directory-3 net_lat: 114
> .......
>
> I wonder, for example, how the smallest latency 'L1Cache-0 -> L1Cache-1
> net_lat: 10' is caculated ?
>  According to the topology file, link latency between two nearby nodes is
> 2 and link latency to L1 cache is only 1. so should the latency between
> two nearby L1 caches around 4 or 5?
>  but it says 10 in the result, what else shall we include?
>
> Thanks a lot!
>
> Xu Han
>
>
>
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