• T
    genirq: Provide forced interrupt threading · 8d32a307
    Thomas Gleixner 提交于
    Add a commandline parameter "threadirqs" which forces all interrupts except
    those marked IRQF_NO_THREAD to run threaded. That's mostly a debug option to
    allow retrieving better debug data from crashing interrupt handlers. If
    "threadirqs" is not enabled on the kernel command line, then there is no
    impact in the interrupt hotpath.
    
    Architecture code needs to select CONFIG_IRQ_FORCED_THREADING after
    marking the interrupts which cant be threaded IRQF_NO_THREAD. All
    interrupts which have IRQF_TIMER set are implict marked
    IRQF_NO_THREAD. Also all PER_CPU interrupts are excluded.
    
    Forced threading hard interrupts also forces all soft interrupt
    handling into thread context.
    
    When enabled it might slow down things a bit, but for debugging problems in
    interrupt code it's a reasonable penalty as it does not immediately
    crash and burn the machine when an interrupt handler is buggy.
    
    Some test results on a Core2Duo machine:
    
    Cache cold run of:
     # time git grep irq_desc
    
          non-threaded       threaded
     real 1m18.741s          1m19.061s
     user 0m1.874s           0m1.757s
     sys  0m5.843s           0m5.427s
    
     # iperf -c server
    non-threaded
    [  3]  0.0-10.0 sec  1.09 GBytes   933 Mbits/sec
    [  3]  0.0-10.0 sec  1.09 GBytes   934 Mbits/sec
    [  3]  0.0-10.0 sec  1.09 GBytes   933 Mbits/sec
    threaded
    [  3]  0.0-10.0 sec  1.09 GBytes   939 Mbits/sec
    [  3]  0.0-10.0 sec  1.09 GBytes   934 Mbits/sec
    [  3]  0.0-10.0 sec  1.09 GBytes   937 Mbits/sec
    Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    LKML-Reference: <20110223234956.772668648@linutronix.de>
    8d32a307
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