Messages in this thread | | | Date | Wed, 18 Apr 2012 17:00:14 +0200 | From | Pascal Chapperon <> | Subject | Re: RCU related performance regression in 3.3 |
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Le 18/04/2012 16:01, Paul E. McKenney a écrit : > On Wed, Apr 18, 2012 at 11:37:28AM +0200, Pascal Chapperon wrote: >> Mount and umount operations are not slower with RCU_FAST_NO_HZ during >> runtime; systemctl start and stop operations are also not slower. In >> fact, i couldn't find a single operation slower during runtime with >> RCU_FAST_NO_HZ. > > Your boot-time setup is such that all CPUs are online before the > boot-time mount operations take place, right? Yes : [ 0.242697] Brought up 8 CPUs [ 0.242699] Total of 8 processors activated (35118.33 BogoMIPS).
> Struggling to understand > how RCU can tell the difference between post-CPU-bringup boot time > and run time... > systemd is controlling the whole boot process including mount operation (apart root filesystem) and as I can see, uses heavily sockets to do it (not to mention cpu-affinity). It controls also the major part of umount operations. Is it possible that your patch hits a systemd bug ? What I don't understand is that systemd coexists well with RCU_FAST_NO_HZ on a smaller laptop with older and much less powerful cpu. I'll do further tests on another machine.
Pascal
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