My implementation of next_pow2_l() was incorrect. e.g. perf record -m4296015872 uname rounding mmap pages size to 17592186044416 bytes (4294967296 pages) Invalid argument for --mmap_pages/-m
Notice that the next power-of-2 value 4294967296 is less than the option value 4296015872. Change to using __builtin_clzl() and prevent the shift being equal to the width of the operand. Also __builtin_clzl(x) is undefined if x is 0, so adjust the condition to preclude that possibility. Now: perf record -m4296015872 uname rounding mmap pages size to 35184372088832 bytes (8589934592 pages) Invalid argument for --mmap_pages/-m Signed-off-by: Adrian Hunter <[email protected]> --- tools/perf/util/util.h | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h index a1eea3e..ae609fe 100644 --- a/tools/perf/util/util.h +++ b/tools/perf/util/util.h @@ -284,13 +284,14 @@ static inline unsigned next_pow2(unsigned x) static inline unsigned long next_pow2_l(unsigned long x) { -#if BITS_PER_LONG == 64 - if (x <= (1UL << 31)) - return next_pow2(x); - return (unsigned long)next_pow2(x >> 32) << 32; -#else - return next_pow2(x); -#endif + int leading_zeros; + + if (x < 2) + return 1; + leading_zeros = __builtin_clzl(x - 1); + if (!leading_zeros) + return 0; + return 1UL << (BITS_PER_LONG - leading_zeros); } size_t hex_width(u64 v); -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
