[Xen-users] RFC: clocksource={xen, tsc} difference between Debian PV and HV

[Philipp Hahn <hahn@xxxxxxxxxxxxx>]

Hello,

while running a simple "sysbench --test=memory run" benchmark I noticed
the following strange behavior: Using "clocksource=tsc" as clock-source
both PV and HV are nearly the same, but with "clocksource=xen" PV is 4-5
times worse than HV. I would have expected the reverse:

Testing Debian-7 PV:
# cd /sys/devices/system/clocksource/clocksource0
# echo xen > current_clocksource && sysbench --test=memory run
    total time:                          634.1719s
# echo tsc > current_clocksource && sysbench --test=memory run
    total time:                          71.2846s

Testing Debian-7 HV:
# cd /sys/devices/system/clocksource/clocksource0
# echo tsc > current_clocksource && sysbench --test=memory run
    total time:                          72.5056s
# echo xen > current_clocksource && sysbench --test=memory run
    total time:                          140.1519s

Is this normal and how can this be explained?

Thanks in advance for any comments.

Philipp Hahn
-- 
Philipp Hahn
Open Source Software Engineer

Univention GmbH
be open.
Mary-Somerville-Str. 1
D-28359 Bremen
Tel.: +49 421 22232-0
Fax : +49 421 22232-99
hahn@xxxxxxxxxxxxx

http://www.univention.de/
GeschÃftsfÃhrer: Peter H. Ganten
HRB 20755 Amtsgericht Bremen
Steuer-Nr.: 71-597-02876

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