Messages in this thread | | | Date | Tue, 13 Jul 2004 17:00:54 +0200 | From | bert hubert <> | Subject | Re: preempt-timing-2.6.8-rc1 |
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On Tue, Jul 13, 2004 at 07:39:47AM -0700, William Lee Irwin III wrote:
> > 49ms non-preemptible critical section violated 1 ms preempt threshold > > starting at snd_pcm_action_lock_irq+0x1b/0x1d0 [snd_pcm] and ending at > > snd_pcm_action_lock_irq+0x65/0x1d0 [snd_pcm]
woa
> > 2) 49ms non-preemptible critical section violated 1 ms preempt threshold > > starting at sys_ioctl+0x42/0x270 and ending at sys_ioctl+0xbd/0x270 > > 40-50 ms most of the time, 12 ms couple of times. > > Let me now if you need those traces for some of these (I've built kernel > > with 8K stacks). > > ioctl() is typically grossly inefficient and even involves the BKL.
Indeed - but 49ms is stunning and worthy of investigation. The interesting thing is that sys_ioctl blankly locks the kernel, even if the systems below it don't need it. Would be a big change to fix.
In this case, how about adding
printk(KERN_DEBUG "ioctl cmd=%d\n", cmd);
here in fs/ioctl.c:
unlock_kernel(); fput(filp);
out: return error; }
Or something else to instrument ioctl?
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