On 11/09/2018 08:13 AM, Arnd Bergmann wrote:
Alas time() calls are simple and in the order of get_res, the cost of which is a five fold improvement over the alternate higher resolution calls (clock_gettime or up to 100 fold on some architectures over gettimeofday). We could measure a small improvement in cpu utilization (and thus battery life by extension) attributed to arm64 Android by calling __kernel_time over __kernel_clock_gettime with coarse resolution. A game of inches admittedly, but super KISS to add, and it is not as-if __kernel_time existencediff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S index beca249bc2f3..9de0ffc369c5 100644 --- a/arch/arm64/kernel/vdso/vdso.lds.S +++ b/arch/arm64/kernel/vdso/vdso.lds.S @@ -88,6 +88,7 @@ VERSION __kernel_gettimeofday; __kernel_clock_gettime; __kernel_clock_getres; + __kernel_time; local: *; }; }I would prefer to not add any deprecated interfaces in the VDSO. If we have the 64-bit version of clock_gettime, we don't need the 32-bit version of it, and we don't need gettimeofday() or time() either. The C library can easily implement those by calling into clock_gettime.
will cause an issue with deprecation of a system call entry point. -- Mark
