[systemd-devel] kdbus performance regression by ~70% on 3.15 kernels ?

[Djalal Harouni]

Hi,

Just to let you know that I did notice a regression by ~70% when running
test-kdbus-benchmark on a kvm guest (that's what I've under hands now)

I know sorry, but still a kdbus on kvm is a valid case, I don't know if
this affects real machine or only kvm guests will be able to confirm it
next week unless someone do!

If you are able to test it in a real machine and confirm that it affects
them too, thank you!
I've managed to bisect this to:
3.15.0-rc1 good
3.15.0-rc5 bad

I Will continue later this day!

Perhaps currently any produced benchmark results for kdbus are not
accurate...!


Busy kvm guest with a fedora filesystem, kernel 3.15.0-rc1
$ ./test/test-kdbus-benchmark 
-- opening /dev/kdbus/control
-- creating bus '1000-testbus'
-- opening bus connection /dev/kdbus/1000-testbus/bus
-- Our peer ID for /dev/kdbus/1000-testbus/bus: 1 -- bus uuid:
'beb14de480b240ccaa1574ffac606ca8'
-- opening bus connection /dev/kdbus/1000-testbus/bus
-- Our peer ID for /dev/kdbus/1000-testbus/bus: 2 -- bus uuid:
'beb14de480b240ccaa1574ffac606ca8'
name_acquire(): flags after call: 0x0
-- entering poll loop ...
stats: 17927 packets processed, latency (usecs) min/max/avg 42/1277/47
stats: 18152 packets processed, latency (usecs) min/max/avg 42/251/46
stats: 18057 packets processed, latency (usecs) min/max/avg 42/441/46
stats: 18152 packets processed, latency (usecs) min/max/avg 42/300/46
stats: 18100 packets processed, latency (usecs) min/max/avg 42/297/46
stats: 18064 packets processed, latency (usecs) min/max/avg 42/239/46



Busy kvm guest with same fedora filesystem (same processes)
but kernel 3.15.0-rc5:

$ ./test/test-kdbus-benchmark 
-- opening /dev/kdbus/control
-- creating bus '1000-testbus'
-- opening bus connection /dev/kdbus/1000-testbus/bus
-- Our peer ID for /dev/kdbus/1000-testbus/bus: 1 -- bus uuid:
'c1433addbdbd4f2e8561c9921d57d112'
-- opening bus connection /dev/kdbus/1000-testbus/bus
-- Our peer ID for /dev/kdbus/1000-testbus/bus: 2 -- bus uuid:
'c1433addbdbd4f2e8561c9921d57d112'
name_acquire(): flags after call: 0x0
-- entering poll loop ...
stats: 5590 packets processed, latency (usecs) min/max/avg 113/10274/131
stats: 5507 packets processed, latency (usecs) min/max/avg 113/10314/132
stats: 5550 packets processed, latency (usecs) min/max/avg 113/12435/132


Thanks

-- 
Djalal Harouni
http://opendz.org