• Thomas Gleixner's avatar
    remove put_cpu_no_resched() · 8b0b1db0
    Thomas Gleixner authored
    put_cpu_no_resched() is an optimization of put_cpu() which unfortunately
    can cause high latencies.
    
    The nfs iostats code uses put_cpu_no_resched() in a code sequence where a
    reschedule request caused by an interrupt between the get_cpu() and the
    put_cpu_no_resched() can delay the reschedule for at least HZ.
    
    The other users of put_cpu_no_resched() optimize correctly in interrupt
    code, but there is no real harm in using the put_cpu() function which is
    an alias for preempt_enable().  The extra check of the preemmpt count is
    not as critical as the potential source of missing a reschedule.
    
    Debugged in the preempt-rt tree and verified in mainline.
    
    Impact: remove a high latency source
    
    [akpm@linux-foundation.org: build fix]
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Acked-by: default avatarIngo Molnar <mingo@elte.hu>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
    Cc: "J. Bruce Fields" <bfields@fieldses.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    8b0b1db0
iostat.h 1.92 KB