• Paul Mackerras's avatar
    powerpc: Improve resolution of VDSO clock_gettime · 597bc5c0
    Paul Mackerras authored
    Currently the clock_gettime implementation in the VDSO produces a
    result with microsecond resolution for the cases that are handled
    without a system call, i.e. CLOCK_REALTIME and CLOCK_MONOTONIC.  The
    nanoseconds field of the result is obtained by computing a
    microseconds value and multiplying by 1000.
    
    This changes the code in the VDSO to do the computation for
    clock_gettime with nanosecond resolution.  That means that the
    resolution of the result will ultimately depend on the timebase
    frequency.
    
    Because the timestamp in the VDSO datapage (stamp_xsec, the real time
    corresponding to the timebase count in tb_orig_stamp) is in units of
    2^-20 seconds, it doesn't have sufficient resolution for computing a
    result with nanosecond resolution.  Therefore this adds a copy of
    xtime to the VDSO datapage and updates it in update_gtod() along with
    the other time-related fields.
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    597bc5c0
vdso_datapage.h 4.16 KB