Messages in this thread |  | | Date | Thu, 5 Jul 2012 17:29:44 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu] Make RCU_FAST_NO_HZ respect nohz= boot parameter |
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On Thu, Jul 05, 2012 at 04:02:08PM -0700, Josh Triplett wrote: > On Thu, Jul 05, 2012 at 03:37:31PM -0700, Paul E. McKenney wrote: > > If the nohz= boot parameter disables nohz, then RCU_FAST_NO_HZ needs to > > also disable itself. This commit therefore checks for tick_nohz_enabled > > being zero, disabling rcu_prepare_for_idle() if so. This patch assumes > > that tick_nohz_enabled can change at runtime: If this is not the case, > > then a simpler approach suffices. > > Allowing nohz to change at runtime seems like an entirely unnecessary > bit of added complexity. (So does having a boot parameter for it, but > that one at least seems easier to handle.)
I will let representatives from the various distros expound to you on their one-binary-only strategy for kernel builds. ;-)
> What would the patch look like if you can assume nohz will never change > at runtime? And does anyone have a use case for changing nohz at > runtime, rather than at boot time?
It would be a little bit simpler, but would break in very odd and difficult-to-debug ways if anyone ever did allow it to change at runtime, for example, to accommodate systems subject to varying workloads.
Thanx, Paul
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