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Message-ID: <CANsc=4X7ThCvgz9bfu1ZZg9FCti5SMdbXL5tA584z-oZ_HEByg@mail.gmail.com>
Date: Wed, 4 Dec 2013 16:12:56 -0500
From: Adrien Vergé <adrienverge@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Russell King <linux@....linux.org.uk>,
Ben Dooks <ben.dooks@...ethink.co.uk>,
Will Deacon <will.deacon@....com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH 0/3] ARM Coresight: Enhance ETM tracing control
2013/12/4 Greg Kroah-Hartman <gregkh@...uxfoundation.org>:
> Your pid implementation is broken, see my other email about that :(
Thank you for your remarks on pid. I'll try to correct that.
> And again, what's wrong with the existing tracing functionalty that is
> processor agnostic? Why can't we just delete this driver today and use
> the existing trace code?
As far as I know, the tracing functionality in
/sys/kernel/debug/tracing does not take advantage of ETM. ETM is a
dedicated hardware that greatly reduces tracing overhead. It only
exists on ARM platforms.
I understand using sysfs here is not the cleanest way. I patched my
kernel to meet my needs (trace a specific process or address range),
and I thought these small modifications could be useful -- until
bigger work is done to remove ETM control from sysfs.
Do you think it's worth correcting my patch (for pid namespaces) and
re-submitting it? Or should we wait for someone to port ETM tracing to
debugfs?
Thanks,
Adrien
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