Messages in this thread | | | Date | Tue, 26 Jan 2010 18:55:16 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH RFC tip/core/rcu] accelerate grace period if last non-dynticked CPU |
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* Andi Kleen (andi@firstfloor.org) wrote: > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes: > > Kind of offtopic to the original patch, but I couldn't > resist... > > > +config RCU_FAST_NO_HZ > > + bool "Accelerate last non-dyntick-idle CPU's grace periods" > > + depends on TREE_RCU && NO_HZ && SMP > > Having such a thing as a config option doesn't really make > any sense to me. Who would want to recompile their kernel > to enable/disable this? If anything it should be runtime, or better > just unconditionally on. > > In general RCU could probably reduce its number of "weird" > Kconfig options. > > While I think I have a better understanding of RCU than a lot > of normal users I often have no clue what to set there when > building a kernel.
Maybe we could keep them under a CONFIG_DEBUG_RCU umbrella. Compiling out parts of the rcu options can be useful for debugging purposes, but I agree with you that end users should not be bothered with that much options when some of them are "obviously" wanted.
OTOH, I understand that Paul seems to want to introduce new RCU features gradually, without hitting all kernel users with bugs in newer features. That's a sane approach to keep things generally stable, but maybe it is time to set some of the stabilized RCU options to default Y and move their config to the debug menu.
Let's see what Paul has to say about this...
Thanks,
Mathieu
> > -Andi > > -- > ak@linux.intel.com -- Speaking for myself only.
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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