Re: [Patch 3/9] Block I/O accounting initialization

From: Arjan van de Ven
Date: Wed Mar 15 2006 - 05:24:37 EST



>
> +static inline void delayacct_blkio_start(void)
> +{
> + if (unlikely(delayacct_on))
> + __delayacct_blkio_start();
> +}


I still think the unlikely() makes no sense here; at runtime it's either
going to be always on or off (in the sense that switching it will be
RARE). The cpus branch predictor will get that right; while if you force
it unlikely you can even run the risk of getting a 100% miss on some
architectures (not x86/x86-64) when you enable the accounting


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