From 20d087368d38c7350a4519a3b316ef7eb2504692 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Fri, 8 Nov 2019 21:34:25 +0100 Subject: time: Optimize ns_to_timespec64() ns_to_timespec64() calls div_s64_rem(), which is a rather slow function on 32-bit architectures, as it cannot take advantage of the do_div() optimizations for constant arguments. Open-code the div_s64_rem() function in ns_to_timespec64(), so a constant divider can be passed into the optimized div_u64_rem() function. Signed-off-by: Arnd Bergmann Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20191108203435.112759-3-arnd@arndb.de --- kernel/time/time.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) (limited to 'kernel/time') diff --git a/kernel/time/time.c b/kernel/time/time.c index 5c54ca632d08..45a358953f09 100644 --- a/kernel/time/time.c +++ b/kernel/time/time.c @@ -550,18 +550,21 @@ EXPORT_SYMBOL(set_normalized_timespec64); */ struct timespec64 ns_to_timespec64(const s64 nsec) { - struct timespec64 ts; + struct timespec64 ts = { 0, 0 }; s32 rem; - if (!nsec) - return (struct timespec64) {0, 0}; - - ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem); - if (unlikely(rem < 0)) { - ts.tv_sec--; - rem += NSEC_PER_SEC; + if (likely(nsec > 0)) { + ts.tv_sec = div_u64_rem(nsec, NSEC_PER_SEC, &rem); + ts.tv_nsec = rem; + } else if (nsec < 0) { + /* + * With negative times, tv_sec points to the earlier + * second, and tv_nsec counts the nanoseconds since + * then, so tv_nsec is always a positive number. + */ + ts.tv_sec = -div_u64_rem(-nsec - 1, NSEC_PER_SEC, &rem) - 1; + ts.tv_nsec = NSEC_PER_SEC - rem - 1; } - ts.tv_nsec = rem; return ts; } -- cgit v1.2.3