Re: [PATCH, RFC, tip/core/rcu] scalable classic RCU implementation

[Ingo Molnar <mingo@elte.hu>]

* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> Is this a sufficient improvement?

yeah - looks much better. This was the block that meets the eye for the 
first time in the patch so it stuck out.

just one more small pet peeve of mine: please use vertical alignment too 
to improve readability. Instead of:

> #define MAX_RCU_LEVELS 3
> #define RCU_FANOUT (CONFIG_RCU_FANOUT)
> #define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT)
> #define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT)

this looks a bit more structured IMO:

> #define MAX_RCU_LEVELS	3
> #define RCU_FANOUT		(CONFIG_RCU_FANOUT)
> #define RCU_FANOUT_SQ		(RCU_FANOUT * RCU_FANOUT)
> #define RCU_FANOUT_CUBE	(RCU_FANOUT_SQ * RCU_FANOUT)

maybe even this:

> #if (NR_CPUS) <= RCU_FANOUT
> #  define NUM_RCU_LVLS	1
> #  define NUM_RCU_LVL_0	1
> #  define NUM_RCU_LVL_1	(NR_CPUS)
> #  define NUM_RCU_LVL_2	0
> #  define NUM_RCU_LVL_3	0
> #elif (NR_CPUS) <= RCU_FANOUT_SQ
> #  define NUM_RCU_LVLS	2
> #  define NUM_RCU_LVL_0	1
> #  define NUM_RCU_LVL_1	(((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT)
> #  define NUM_RCU_LVL_2	(NR_CPUS)
> #  define NUM_RCU_LVL_3	0
> #elif (NR_CPUS) <= RCU_FANOUT_CUBE
> #  define NUM_RCU_LVLS	3
> #  define NUM_RCU_LVL_0	1
> #  define NUM_RCU_LVL_1	(((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ)
> #  define NUM_RCU_LVL_2	(((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT))
> #  define NUM_RCU_LVL_3	NR_CPUS
> #else
> # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
> #endif /* #if (NR_CPUS) <= RCU_FANOUT */

but no strong feelings on that one. (maybe inserting a space at the 
right places helps too, no need for a full tab)

	Ingo