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Re: [Xen-devel] Re: [PATCH] add long interrupt measurement capability

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH] add long interrupt measurement capability
From: Dulloor <dulloor@xxxxxxxxx>
Date: Tue, 19 May 2009 00:41:17 -0400
Cc: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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Hi Keir,

Can you consider this for check-in.


2009/5/11 Dulloor <dulloor@xxxxxxxxx>
- Changed the name to trace_irq :)

- trace_irq dumps just tsc_in and tsc_out values in a single record. I guess there is no need to write two records (wasting trace-buf mem, more processing, additional logic in xentrace and/or xentrace_format).

- xentrace_format does what Dan wanted.


2009/5/11 Tian, Kevin <kevin.tian@xxxxxxxxx>

I guess you can handle it much simpler by stamping a record in both irq_enter and irq_exit. All the statistics jobs are left for xentrace script to digest.
Also I'd call it as trace_irq instead of trace_guest_irq. :-)

From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Dulloor
Sent: 2009年5月9日 17:12
To: Keir Fraser
Cc: Ian Pratt; Xen-Devel (E-mail); Dan Magenheimer

Subject: Re: [Xen-devel] Re: [PATCH] add long interrupt measurement capability

Here is a xentrace patch.

- Should irq_desc_measure_t move to some .h file ?
- I have defined the new trace event in general class. Is it fine ?

- I have defined tsc_in as volatile to avoid initializing it in the main code path.


On Sat, May 9, 2009 at 3:56 AM, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:
On 08/05/2009 22:53, "Ian Pratt" <Ian.Pratt@xxxxxxxxxxxxx> wrote:

>> Perhaps.  However measuring cycles is important and, more
>> specifically, measuring MAX cycles spent across a set of
>> interrupts.  As a result, I suspect any code that measures
>> this (regardless of whether the result is reported by
>> xentrace or debug-key) would likely encounter the
>> same objection from Keir.
> I can't imagine there'd be any objection to adding trace macros to record
> this. The xentrace log processing tool can then be updated to generate max or
> histogram values.

Yes, xentrace records would be okay. It's adding another debug key and
printing to Xen console for this purpose which I do not think is worthwhile.

 -- Keir

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