From: Will Deacon <will.deacon@arm.com>
To: Srinivas Ramana <sramana@codeaurora.org>
Cc: catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] trace: extend trace_clock to support arch_arm clock counter
Date: Fri, 2 Dec 2016 11:08:45 +0000 [thread overview]
Message-ID: <20161202110845.GC8266@arm.com> (raw)
In-Reply-To: <1480666495-26536-1-git-send-email-sramana@codeaurora.org>
On Fri, Dec 02, 2016 at 01:44:55PM +0530, Srinivas Ramana wrote:
> Extend the trace_clock to support the arch timer cycle
> counter so that we can get the monotonic cycle count
> in the traces. This will help in correlating the traces with the
> timestamps/events in other subsystems in the soc which share
> this common counter for driving their timers.
I'm not sure I follow this reasoning. What's wrong with nanoseconds? In
particular, the "perf" trace_clock hangs off sched_clock, which should
be backed by the architected counter anyway. What does the cycle counter in
isolation tell you, given that the frequency isn't architected?
I think I'm missing something here.
Will
WARNING: multiple messages have this Message-ID (diff)
From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] trace: extend trace_clock to support arch_arm clock counter
Date: Fri, 2 Dec 2016 11:08:45 +0000 [thread overview]
Message-ID: <20161202110845.GC8266@arm.com> (raw)
In-Reply-To: <1480666495-26536-1-git-send-email-sramana@codeaurora.org>
On Fri, Dec 02, 2016 at 01:44:55PM +0530, Srinivas Ramana wrote:
> Extend the trace_clock to support the arch timer cycle
> counter so that we can get the monotonic cycle count
> in the traces. This will help in correlating the traces with the
> timestamps/events in other subsystems in the soc which share
> this common counter for driving their timers.
I'm not sure I follow this reasoning. What's wrong with nanoseconds? In
particular, the "perf" trace_clock hangs off sched_clock, which should
be backed by the architected counter anyway. What does the cycle counter in
isolation tell you, given that the frequency isn't architected?
I think I'm missing something here.
Will
next prev parent reply other threads:[~2016-12-02 11:08 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-02 8:14 [PATCH] trace: extend trace_clock to support arch_arm clock counter Srinivas Ramana
2016-12-02 8:14 ` Srinivas Ramana
2016-12-02 11:08 ` Will Deacon [this message]
2016-12-02 11:08 ` Will Deacon
2016-12-04 8:34 ` Srinivas Ramana
2016-12-04 8:36 ` Srinivas Ramana
2016-12-04 8:36 ` Srinivas Ramana
2016-12-06 12:13 ` Will Deacon
2016-12-06 12:13 ` Will Deacon
2016-12-06 12:13 ` Will Deacon
2016-12-12 5:01 ` Srinivas Ramana
2016-12-12 5:01 ` Srinivas Ramana
2016-12-12 10:42 ` Will Deacon
2016-12-12 10:42 ` Will Deacon
2016-12-15 13:16 ` Srinivas Ramana
2016-12-15 13:16 ` Srinivas Ramana
2016-12-20 17:04 ` Will Deacon
2016-12-20 17:04 ` Will Deacon
2016-12-30 19:15 ` Stephen Boyd
2016-12-30 19:15 ` Stephen Boyd
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