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Date: Fri, 30 Dec 2005 08:36:39 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Lee Revell <rlrevell@joe-job.com>
Cc: kus Kusche Klaus <kus@keba.com>,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Latency traces I cannot interpret (sa1100, 2.6.15-rc7-rt1)
Message-ID: <20051230073639.GA25637@elte.hu>
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* Lee Revell <rlrevell@joe-job.com> wrote:

> > However, traces 1, 2, 6 and 7 are completely mysterious to me.
> > Interrupts seem to be blocked for milliseconds, while nothing is going
> > on on the system? Moreover, there are console-related function names
> > in
> > traces 6 and 7, although I've unconfigured the framebuffer console for
> > these runs!
> 
> It seems that either some code path really is forgetting to re-enable 
> interrupts, or there's a bug in the latency tracer.

one question is, what do the kernel addresses visible in the first 
argument of asm_do_IRQ() correspond to:

 trace1:MyThread-153   0D..1 5977us+: asm_do_IRQ (c030c170 1a 0)
 trace1:MyThread-153   0D..1 15191us+: asm_do_IRQ (c030c1bc 1a 0)
 trace2:  <idle>-0     0D..2 8822us+: asm_do_IRQ (c021da24 1a 0)
 trace2:  <idle>-0     0Dn.2 8920us+: asm_do_IRQ (c021da24 b 0)
 trace3:     top-169   0D..1 8802us+: asm_do_IRQ (c024e5fc 1a 0)
 trace4:  insmod-185   0D..1 8794us+: asm_do_IRQ (c030c174 1a 0)
 trace5:      dd-197   0D..1 8812us+: asm_do_IRQ (c02e4938 1a 0)
 trace6: kthread-11    0d..3 2670us+: asm_do_IRQ (c02fe2d0 1a 0)
 trace7:MyThread-95    0D..1  542us+: asm_do_IRQ (c02fe2d0 1a 0)
 trace7:MyThread-95    0D..1 9755us+: asm_do_IRQ (c02fe2d0 1a 0)

i.e. what is c02fe2d0, c021da24, c02e4938, etc.?

but it seems most of the latencies are printk related: one possibility 
is that something is doing a costly printk with preemption disabled.

	Ingo
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