[Xen-devel] [PATCH]Improve ttcp performance for domUs

[Stephan Diestelhorst <sd386@xxxxxxxxxxxx>]

Recent tests on the default setup of domains in sedf showed a dramatic 
slowdown in network performance (namely ttcp). I did some benchmarks, 
results:
(machine is a dual Xeon, but I used noht and nosmp to emulate uniproc. 
performance, network is 1Gb/s)

domU->external
external: ttcp -r -s  -fm -l 131072
domU: ttcp external -t -s -fm -l 131072 -n 8192 

bvt (default): 385.07 Mbit/s!
sedf (default, i.e. dom0: 15/20, domU: weight 1): 294.15 Mbit/sec 
sedf(dom0: 5/20, domU: weight 1): 366.93 Mbit/sec
sedf(dom0: 5/20, domU: 5/20) 411.72 Mbit/sec

=> Set dom0 by default to 5/20 restores most of the performance (actually 
setting it even lower should increase performance further, because more 
batching will occur! quick test of 3/20 revealed: 395 Mb/s, but it might 
impact latency!)

Signed-off by: Stephan.Diestelhorst@{cl.cam.ac.uk, inf.tu-dresden.de}

Attachment: fix_defaults_sedf2.patch
Description: Text Data

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