Re: kernbench on 512p

[Manfred Spraul]

Greg Edwards wrote:

> | >
> | Which value did you use for RCU_GROUP_SIZE? I'm not sure what's the 
> | optimal value for 512p - probably 32 or so.
>
> I used what was defined in the patch
>
> +#define RCU_GROUP_SIZE 2
>
> I can try running with a couple different values and see how it looks.
>
>  
Ok, that explains the lockstat: I've missed data on rcu_group_state.lock.

I'd just use 32. The code uses a two-level bitmap and the group size 
specifies the size of the lower level.
Thus you use right now a 2/256 split. Therefore you still trash the 
spinlock that protects the upper level. Group size 32 would generate a 
32/16 split.

--
   Manfred

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