[gem5-users] Re: Garnet3.0: huge latency of packets

[赵子丰]

Hi everyone,


I searched similar problems in the ealier mesages list. And I learn about the 
reason why 
the latency of packets is so high. The parameter "sim-cycles" actually means 
that simulation ticks,
rather than cycles. Also, the unit of average_packets_latency in the stats.txt 
is "Tick" , not "Cycle"! 


ZiFeng Zhao
 
------------------ Original ------------------
From: &nbsp;"赵子丰"<22112020...@m.fudan.edu.cn&gt;;
Date: &nbsp;Tue, Sep 27, 2022 11:29 AM
To: &nbsp;"gem5-users"<gem5-users@gem5.org&gt;; 

Subject: &nbsp;Garnet3.0: huge latency of packets 

&nbsp;

Dear all, 
(My last email content has many char '&amp;nbsp'. In order to make it easy to 
read,&nbsp; I delete these chars in this letter.
I am new to the Garnet model. After I followed the command on the 'garnet 
synthetic traffic' website, 
I found that the packets have a very high latency, like this:
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
system.ruby.network.average_flit_latency6250(Unspecified)
system.ruby.network.average_flit_network_latency5250(Unspecified)
system.ruby.network.average_flit_queueing_latency1000(Unspecified)
system.ruby.network.average_flit_vnet_latency |5250|nan|nan(Unspecified)
system.ruby.network.average_flit_vqueue_latency |1000|nan|nan(Unspecified)
system.ruby.network.average_hops3.750000(Unspecified)
system.ruby.network.average_packet_latency6250(Unspecified)
system.ruby.network.average_packet_network_latency5250(Unspecified)
system.ruby.network.average_packet_queueing_latency1000(Unspecified)
system.ruby.network.average_packet_vnet_latency |5250|nan|nan(Unspecified)
system.ruby.network.average_packet_vqueue_latency |1000|nan|nan(Unspecified)

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Then I checked the number of packets which were injected to the Mesh network. 
The statistics result is listed below:
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
system.ruby.network.packets_injected|10100.00% 100.00% |0 0.00% 100.00% | 0 
0.00% 100.00%(Unspecified)
system.ruby.network.packets_injected::total&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 
&nbsp;10&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 
&nbsp; &nbsp;(Unspecified)
system.ruby.network.packets_received&nbsp; &nbsp; &nbsp;|4 100.00% 100.00% | 0 
0.00% 100.00% | 0 0.00% 100.00% (Unspecified)
system.ruby.network.packets_received::total 4

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
the command I used is:
./build/NULL/gem5.opt configs/example/garnet_synth_traffic.py --network=garnet 
--num-cpus=64 --num-dirs=64 
--topology=Mesh_XY --mesh-rows=8 --sim-cycles=10000 --inj-vnet=0 
--injectionrate=0.02 --synthetic=uniform_random


I have tried run the cmd in gem5 v21.2.1.0 and v22.0.0.2, respectly. The result 
is same.
Why so few packets can be injected to the network? And why the latency of 
packets is so huge? I guess some congestion happend in the network. 


Thanks a lot.


ZiFeng Zhao
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