On 12/01/2016 02:12 PM, Tom Herbert wrote:
We have consider both request size and response side in RPC.
Presumably, something like a memcache server is most serving data as
opposed to reading it, we are looking to receiving much smaller
packets than being sent. Requests are going to be quite small say 100
bytes and unless we are doing significant amount of pipelining on
connections GRO would rarely kick-in. Response size will have a lot of
variability, anything from a few kilobytes up to a megabyte. I'm sorry
I can't be more specific this is an artifact of datacenters that have
100s of different applications and communication patterns. Maybe 100b
request size, 8K, 16K, 64K response sizes might be good for test.

No worries on the specific sizes, it is a classic "How long is a piece of string?" sort of question.

Not surprisingly, as the size of what is being received grows, so too the delta between GRO on and off.

stack@np-cp1-c0-m1-mgmt:~/rjones2$ HDR="-P 1"; for r in 8K 16K 64K 1M; do for gro in on off; do sudo ethtool -K hed0 gro ${gro}; brand="$r gro $gro"; ./netperf -B "$brand" -c -H np-cp1-c1-m3-mgmt -t TCP_RR $HDR -- -P 12867 -r 128,${r} -o result_brand,throughput,local_sd; HDR="-P 0"; done; done MIGRATED TCP REQUEST/RESPONSE TEST from ( port 12867 AF_INET to np-cp1-c1-m3-mgmt () port 12867 AF_INET : demo : first burst 0
Result Tag,Throughput,Local Service Demand
"8K gro on",9899.84,35.947
"8K gro off",7299.54,61.097
"16K gro on",8119.38,58.367
"16K gro off",5176.87,95.317
"64K gro on",4429.57,110.629
"64K gro off",2128.58,289.913
"1M gro on",887.85,918.447
"1M gro off",335.97,3427.587

So that gives a feel for by how much this alternative mechanism would have to reduce path-length to maintain the CPU overhead, were the mechanism to preclude GRO.


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