On Sep 14, 2016, at 1:28 PM, Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
>
> We can use ilog2() to more easily produce the desired NR_BG_LOCKS. This
> works because ilog2() is evaluated at compile-time when its argument is
> a compile-time constant.
>
> I did not change the chosen NR_BG_LOCKS values.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
> ---
> include/linux/blockgroup_lock.h | 22 ++--------------------
> 1 file changed, 2 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/blockgroup_lock.h b/include/linux/blockgroup_lock.h
> index 61b583d..225bdb7 100644
> --- a/include/linux/blockgroup_lock.h
> +++ b/include/linux/blockgroup_lock.h
> @@ -10,28 +10,10 @@
> #include <linux/cache.h>
>
> #ifdef CONFIG_SMP
> -
> -/*
> - * We want a power-of-two. Is there a better way than this?
> - */
> -
> -#if NR_CPUS >= 32
> -#define NR_BG_LOCKS 128
> -#elif NR_CPUS >= 16
> -#define NR_BG_LOCKS 64
> -#elif NR_CPUS >= 8
> -#define NR_BG_LOCKS 32
> -#elif NR_CPUS >= 4
> -#define NR_BG_LOCKS 16
> -#elif NR_CPUS >= 2
> -#define NR_BG_LOCKS 8
> +#define NR_BG_LOCKS (4 << ilog2(NR_CPUS < 32 ? NR_CPUS : 32))
> #else
> -#define NR_BG_LOCKS 4
> -#endif
> -
> -#else /* CONFIG_SMP */
> #define NR_BG_LOCKS 1
> -#endif /* CONFIG_SMP */
> +#endif
>
> struct bgl_lock {
> spinlock_t lock;
> --
> 2.8.0.rc3.226.g39d4020
>
Cheers, Andreas
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