"Paul E. McKenney" <paul...@linux.vnet.ibm.com> writes: > On Thu, Mar 21, 2013 at 10:41:30AM -0700, Arjan van de Ven wrote: >> On 3/21/2013 10:18 AM, Paul E. McKenney wrote: >> > o Use the "idle=poll" boot parameter. However, please note >> > that use of this parameter can cause your CPU to overheat, >> > which may cause thermal throttling to degrade your >> > latencies --and that this degradation can be even worse >> > than that of dyntick-idle. >> >> it also disables (effectively) Turbo Mode on Intel cpus... which can >> cost you a serious percentage of performance > > Thank you, added! Please see below for the updated list. > > Thanx, Paul > > ------------------------------------------------------------------------ > > o Dyntick-idle slows transitions to and from idle slightly. > In practice, this has not been a problem except for the most > aggressive real-time workloads, which have the option of disabling > dyntick-idle mode, an option that most of them take. However, > some workloads will no doubt want to use adaptive ticks to > eliminate scheduling-clock-tick latencies. Here are some > options for these workloads: > > a. Use PMQOS from userspace to inform the kernel of your > latency requirements (preferred).
This is not only the preferred approach, but the *only* approach available on non-x86 systems. Perhaps the others should be marked as x86-only? Kevin > b. Use the "idle=mwait" boot parameter. > > c. Use the "intel_idle.max_cstate=" to limit the maximum > depth C-state depth. > > d. Use the "idle=poll" boot parameter. However, please note > that use of this parameter can cause your CPU to overheat, > which may cause thermal throttling to degrade your > latencies -- and that this degradation can be even worse > than that of dyntick-idle. Furthermore, this parameter > effectively disables Turbo Mode on Intel CPUs, which > can significantly reduce maximum performance. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
