Change Details

Patch was tested on SandyBridge, amd64 kernel, both with 64 and 32 bit libc. The syscall_timing tool measurements results are below. Note that RDTSC with syscall is faster than userspace HPET access. But still, userspace HPET is four times faster than syscall HPET. ``` TSC/fast_gettime Clock resolution: 0.000000001 test loop time iterations periteration gettimeofday 0 1.007928510 52591682 0.000000019 gettimeofday 1 1.043998478 54486193 0.000000019 gettimeofday 2 1.043989482 54433115 0.000000019 gettimeofday 3 1.043997933 54474925 0.000000019 gettimeofday 4 1.040992803 53948267 0.000000019 gettimeofday 5 1.043994609 54500053 0.000000019 gettimeofday 6 1.020053741 53194581 0.000000019 gettimeofday 7 1.043989787 54482331 0.000000019 gettimeofday 8 1.043994915 54525097 0.000000019 gettimeofday 9 1.031130020 53843960 0.000000019 HPET/fast_gettime Clock resolution: 0.000000070 test loop time iterations periteration gettimeofday 0 1.000992061 1723026 0.000000580 gettimeofday 1 1.000910519 1721538 0.000000581 gettimeofday 2 1.000068005 1720167 0.000000581 gettimeofday 3 1.001043273 1720474 0.000000581 gettimeofday 4 1.000974022 1723124 0.000000580 gettimeofday 5 1.000955265 1721566 0.000000581 gettimeofday 6 1.004998299 1728666 0.000000581 gettimeofday 7 1.043984721 1794984 0.000000581 gettimeofday 8 1.035997777 1783213 0.000000580 gettimeofday 9 1.047979740 1802630 0.000000581 syscall/TSC Clock resolution: 0.000000001 test loop time iterations periteration gettimeofday 0 1.004486363 3588937 0.000000279 gettimeofday 1 1.042046225 3721676 0.000000279 gettimeofday 2 1.025922097 3661175 0.000000280 gettimeofday 3 1.012252698 3615760 0.000000279 gettimeofday 4 1.021744804 3649573 0.000000279 gettimeofday 5 1.043990357 3702818 0.000000281 gettimeofday 6 1.043995558 3725780 0.000000280 gettimeofday 7 1.043994414 3727664 0.000000280 gettimeofday 8 1.022993828 3653711 0.000000279 gettimeofday 9 1.043989137 3729411 0.000000279 syscall/HPET Clock resolution: 0.000000070 test loop time iterations periteration gettimeofday 0 1.024957696 414023 0.000002475 gettimeofday 1 1.001028436 404051 0.000002477 gettimeofday 2 1.023964920 413640 0.000002475 gettimeofday 3 1.004981756 406646 0.000002471 gettimeofday 4 1.007988443 408052 0.000002470 gettimeofday 5 1.001993736 404759 0.000002475 gettimeofday 6 1.043990521 422299 0.000002472 gettimeofday 7 1.030991827 416968 0.000002472 gettimeofday 8 1.011988548 408502 0.000002477 gettimeofday 9 1.017240226 406376 0.000002503 ```