linux-kernel - Re: [PATCH] tracing/events: Add bounce tracing to swiotbl-xen

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Date:	Wed, 4 Sep 2013 21:10:50 +0100
From:	Zoltan Kiss <zoltan.kiss@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xensource.com>,
	<virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH] tracing/events: Add bounce tracing to swiotbl-xen

On 03/09/13 13:42, Konrad Rzeszutek Wilk wrote:
> Correct. The double buffering code is being run in lib/swiotlb.c not the
> xen-swiotlb.c. Hence the question of why not move the tracing in there.
I've put the trace to both locations before swiotlb_tbl_map_single is 
called, so the same tracer will be hit both with classic and Xen 
SWIOTLB. I used 2 different place instead of calling from 
swiotlb_tbl_map_single because I want to print out dev_addr, and it's 
calculated differently.

> Yes. And please (if it adds a benefit) also for unmap/sync which can trigger
> the bounce buffer.
>
> Or if it makes sense just for the bounce buffer copying - then just
> leave it at that. Thanks.
For me the relevant event was to see when we start to do bounce 
buffering. When does it end, or when syncing happens is a different 
thing. If someone is interested, they can easily extend this patch with 
that.

However one question bothers me: why ftrace doesn't trace these 
functions? They are not inlined, static, or marked as notrace.

Regards,

Zoli
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