From: gregkh@linuxfoundation.org (Greg Kroah-Hartman)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/3] ARM Coresight: Enhance ETM tracing control
Date: Wed, 4 Dec 2013 20:01:04 -0800 [thread overview]
Message-ID: <20131205040104.GA14641@kroah.com> (raw)
In-Reply-To: <CANsc=4UGi5sMdUW5qQDzEJx4h8NDU+-b=xOLBAZtzbV5ugz3Fg@mail.gmail.com>
On Wed, Dec 04, 2013 at 10:49:25PM -0500, Adrien Verg? wrote:
> 2013/12/4 Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
> > How much overhead does the existing tracing code have on ARM? Is ETM
> > still even needed? Why not just use ETM for the core tracing code
> > instead?
>
> Coresight ETM is not just faster than /sys/kernel/debug/tracing, it
> provides more detailed and customisable info. For instance, you can
> trace every load, store, instruction fetch, along with the number of
> cycles taken, with almost zero-overhead.
Can't you already do that with the 'perf' tool the kernel provides
without the ETM driver?
> > What's wrong with the in-kernel tracing logic that you can't use that
> > instead of the ETM stuff?
>
> ETM has a different purpose. Integrating it in
> /sys/kernel/debug/tracing would not take advantage of all its
> features.
What is it's purpose then? At first glance, this seems to be exactly
what 'perf' provides already. Doesn't perf work on ARM today?
thanks,
greg k-h
WARNING: multiple messages have this Message-ID (diff)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: "Adrien Vergé" <adrienverge@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Russell King <linux@arm.linux.org.uk>,
Ben Dooks <ben.dooks@codethink.co.uk>,
Will Deacon <will.deacon@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
"zhangwei(Jovi)" <jovi.zhangwei@huawei.com>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH 0/3] ARM Coresight: Enhance ETM tracing control
Date: Wed, 4 Dec 2013 20:01:04 -0800 [thread overview]
Message-ID: <20131205040104.GA14641@kroah.com> (raw)
In-Reply-To: <CANsc=4UGi5sMdUW5qQDzEJx4h8NDU+-b=xOLBAZtzbV5ugz3Fg@mail.gmail.com>
On Wed, Dec 04, 2013 at 10:49:25PM -0500, Adrien Vergé wrote:
> 2013/12/4 Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
> > How much overhead does the existing tracing code have on ARM? Is ETM
> > still even needed? Why not just use ETM for the core tracing code
> > instead?
>
> Coresight ETM is not just faster than /sys/kernel/debug/tracing, it
> provides more detailed and customisable info. For instance, you can
> trace every load, store, instruction fetch, along with the number of
> cycles taken, with almost zero-overhead.
Can't you already do that with the 'perf' tool the kernel provides
without the ETM driver?
> > What's wrong with the in-kernel tracing logic that you can't use that
> > instead of the ETM stuff?
>
> ETM has a different purpose. Integrating it in
> /sys/kernel/debug/tracing would not take advantage of all its
> features.
What is it's purpose then? At first glance, this seems to be exactly
what 'perf' provides already. Doesn't perf work on ARM today?
thanks,
greg k-h
next prev parent reply other threads:[~2013-12-05 4:01 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-04 4:39 [PATCH 0/3] ARM Coresight: Enhance ETM tracing control Adrien Vergé
2013-12-04 4:39 ` Adrien Vergé
2013-12-04 7:04 ` Greg Kroah-Hartman
2013-12-04 7:04 ` Greg Kroah-Hartman
2013-12-04 16:52 ` Adrien Vergé
2013-12-04 16:52 ` Adrien Vergé
2013-12-04 17:07 ` Greg Kroah-Hartman
2013-12-04 17:07 ` Greg Kroah-Hartman
2013-12-04 21:12 ` Adrien Vergé
2013-12-04 21:12 ` Adrien Vergé
2013-12-04 23:02 ` Greg Kroah-Hartman
2013-12-04 23:02 ` Greg Kroah-Hartman
2013-12-05 3:49 ` Adrien Vergé
2013-12-05 3:49 ` Adrien Vergé
2013-12-05 4:01 ` Greg Kroah-Hartman [this message]
2013-12-05 4:01 ` Greg Kroah-Hartman
2013-12-05 20:12 ` Christopher Covington
2013-12-05 20:12 ` Christopher Covington
2013-12-05 20:16 ` Greg Kroah-Hartman
2013-12-05 20:16 ` Greg Kroah-Hartman
2013-12-05 22:45 ` Christopher Covington
2013-12-05 22:45 ` Christopher Covington
2013-12-05 23:26 ` Greg Kroah-Hartman
2013-12-05 23:26 ` Greg Kroah-Hartman
2013-12-05 23:54 ` Adrien Vergé
2013-12-05 23:54 ` Adrien Vergé
2013-12-06 0:06 ` Greg Kroah-Hartman
2013-12-06 0:06 ` Greg Kroah-Hartman
2013-12-06 0:23 ` Russell King - ARM Linux
2013-12-06 0:23 ` Russell King - ARM Linux
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