Re: [PATCH] blockgroup_lock.h: simplify definition of NR_BG_LOCKS
From: Andreas Dilger <hidden>
Date: 2016-09-14 21:09:36
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On Sep 14, 2016, at 1:28 PM, Eric Biggers [off-list ref] 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 <redacted>
Reviewed-by: Andreas Dilger <redacted>
quoted hunk ↗ jump to hunk
--- 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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