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    powerpc: Fix accounting of softirq time when idle · ad5d1c88
    Anton Blanchard 提交于
    commit cf9efce0 (powerpc: Account time using timebase rather
    than PURR) used in_irq() to detect if the time was spent in
    interrupt processing. This only catches hardirq context so if we
    are in softirq context and in the idle loop we end up accounting it
    as idle time. If we instead use in_interrupt() we catch both softirq
    and hardirq time.
    
    The issue was found when running a network intensive workload. top
    showed the following:
    
    0.0%us,  1.1%sy,  0.0%ni, 85.7%id,  0.0%wa,  9.9%hi,  3.3%si,  0.0%st
    
    85.7% idle. But this was wildly different to the perf events data.
    To confirm the suspicion I ran something to keep the core busy:
    
    # yes > /dev/null &
    
    8.2%us,  0.0%sy,  0.0%ni,  0.0%id,  0.0%wa, 10.3%hi, 81.4%si,  0.0%st
    
    We only got 8.2% of the CPU for the userspace task and softirq has
    shot up to 81.4%.
    
    With the patch below top shows the correct stats:
    
    0.0%us,  0.0%sy,  0.0%ni,  5.3%id,  0.0%wa, 13.3%hi, 81.3%si,  0.0%st
    Signed-off-by: NAnton Blanchard <anton@samba.org>
    Cc: stable@kernel.org
    Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
    ad5d1c88
time.c 29.9 KB