• Thomas Gleixner's avatar
    x86/ioperm: Add bitmap sequence number · 060aa16f
    Thomas Gleixner authored
    Add a globally unique sequence number which is incremented when ioperm() is
    changing the I/O bitmap of a task. Store the new sequence number in the
    io_bitmap structure and compare it with the sequence number of the I/O
    bitmap which was last loaded on a CPU. Only update the bitmap if the
    sequence is different.
    
    That should further reduce the overhead of I/O bitmap scheduling when there
    are only a few I/O bitmap users on the system.
    
    The 64bit sequence counter is sufficient. A wraparound of the sequence
    counter assuming an ioperm() call every nanosecond would require about 584
    years of uptime.
    Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    060aa16f
process.c 24.6 KB