Messages in this thread | | | Date | Tue, 26 Jan 2010 21:21:33 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH RFC tip/core/rcu] accelerate grace period if last non-dynticked CPU |
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On Tue, Jan 26, 2010 at 06:55:16PM -0500, Mathieu Desnoyers wrote: > * 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.
That is indeed a big part of the motivation. ;-)
Thanx, Paul
> 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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