For this system (amd) the only thing that seems to make a difference is the idle=poll (no-halt seems to have no effect)
I go from 200+us latency to 7us top. sam On 2/13/2013 11:29 AM, Michael Haberler wrote: > for reference - from > http://www.kernel.org/doc/Documentation/kernel-parameters.txt > > nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or > wfi(ARM) instruction doesn't work correctly and not to > use it. This is also useful when using JTAG debugger. > > no-hlt [BUGS=X86-32] Tells the kernel that the hlt > instruction doesn't work correctly and not to > use it. > > idle= [X86] > Format: idle=poll, idle=mwait, idle=halt, > idle=nomwait > Poll forces a polling idle loop that can slightly > improve the performance of waking up a idle CPU, but > will use a lot of power and make the system run hot. > Not recommended. > idle=mwait: On systems which support MONITOR/MWAIT > but > the kernel chose to not use it because it doesn't > save > as much power as a normal idle loop, use the > MONITOR/MWAIT idle loop anyways. Performance should > be > the same as idle=poll. > idle=halt: Halt is forced to be used for CPU idle. > In such case C2/C3 won't be used again. > idle=nomwait: Disable mwait for CPU C-states > > it seems from the above for x86 the combination would be > > no-hlt idle=poll > > as for an ARM, it would be > > nohlt idle=poll > > > It would be value to explore the arguments to idle= a bit more on 'laggy' x86 > platforms, in particular the combinations: > > no-hlt idle=mwait > no-hlt idle=nomwait > > assuming the combination 'no-hlt idle=halt' is contradictory > > on ARM's, only 'nohlt' makes sense assuming the documentation is correct > > > --- > > It seems to be about power saving modes > > an overview of CPU C* states is here: > http://www.hardwaresecrets.com/article/611 > > > - Michael > ------------------------------------------------------------------------------ > Free Next-Gen Firewall Hardware Offer > Buy your Sophos next-gen firewall before the end March 2013 > and get the hardware for free! Learn more. > http://p.sf.net/sfu/sophos-d2d-feb > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > > ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
