From: Andrew J. <dr...@re...> - 2013-10-15 14:45:25
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----- Original Message ----- > Hi! > > > The problem with the test is that it tries to assert that granurality of > > > gerusage CPU time accounting is as good as possible. The granularity > > > itself depends on kernel config options, mainly on CONFIG_HZ. But as the > > > kernel compilation options are not exported (by running kernel) in any > > > reliable way the code I've added tries to guess them by side channel > > > (the CLOCK_REALTIME_COARSE resolution). If CLOCK_REALTIME_COARSE is not > > > supported it goes with 4ms which should correspond with CONFIG_HZ=250. > > > > > > Now the accuracy on xen may be off for several reasons. It can have > > > CONFIG_HZ=100. Or xen may not be able to account virtual CPU time with > > > the same accuracy as on the real CPU... > > > > Drew (from xen team) mentioned something along these lines as well. > > > > Do we have some simple way to detect that test is running on xen > > (dom0/domU), > > so we could end test with TCONF in that case? > > I'm not aware of any. But feel free to add a function into LTP lib/. xen dom0 and guests (rhel5 anyway) will have a /proc/xen dir that can checked for. drew > > -- > Cyril Hrubis > ch...@su... > |