Re: [PATCH] percpu_counter: FBC_BATCH might be too big

From: David Miller
Date: Fri Dec 05 2008 - 15:32:20 EST

From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Date: Fri, 05 Dec 2008 17:05:16 +0100

> For NR_CPUS >= 16 values, FBC_BATCH is 2*NR_CPUS
> Considering more and more distros are using high NR_CPUS values,
> it makes sense to use a more sensible value for FBC_BATCH.
> A sensible value is 2*num_online_cpus(), with a minimum value of 32
> (This minimum value helps branch prediction in __percpu_counter_add())
> We already have a hotcpu notifier, so we can adjust FBC_BATCH dynamically.
> Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>

The downside is now we must load this value in these common
routines. But I think the gain outweights the loss so:

Acked-by: David S. Miller <davem@xxxxxxxxxxxxx>
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