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Message-ID: <20090115140454.GH4722@google.com>
Date: Thu, 15 Jan 2009 06:04:55 -0800
From: Mandeep Singh Baines <msb@...gle.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: linux-kernel@...r.kernel.org, rientjes@...gle.com,
mbligh@...gle.com, thockin@...gle.com, akpm@...ux-foundation.org,
netdev@...r.kernel.org
Subject: Re: [PATCH] softlockup: detect bottom-half lockups
Stumbled upon ftrace tracepoints while writing this patch. Should
make life a lot easier for debugging latency issues.
bhlockup should complement ftrace. Once you've found that there's a
problem, tracing can be a big help in debugging. But assertions are
nice for finding problems you didn't know exist.
Ingo Molnar (mingo@...e.hu) wrote:
>
> * Mandeep Singh Baines <msb@...gle.com> wrote:
>
> > The feature should be useful to real-time developers and developers of
> > network and other high-performance drivers.
>
> hm, did you know about the ftrace latency tracers:
>
> config IRQSOFF_TRACER
> bool "Interrupts-off Latency Tracer"
>
> config PREEMPT_TRACER
> bool "Preemption-off Latency Tracer"
>
> config SCHED_TRACER
> bool "Scheduling Latency Tracer"
>
> PREEMPT_TRACER would have shown you that softirqs-off section very nicely.
>
> (And if you also enable the function tracer then not just the latency
> endpoint is shown, but also all the function calls that happened in the
> critical section.)
>
> Ingo
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