From: Peter Zijlstra <peterz@infradead.org>
To: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Russell King <linux@arm.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Aaron Tomlin <atomlin@redhat.com>, Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@osdl.org>,
Daniel Thompson <daniel.thompson@linaro.org>,
x86@kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH v2 4/4] nmi_backtrace: generate one-line reports for idle cpus
Date: Mon, 21 Mar 2016 18:17:38 +0100 [thread overview]
Message-ID: <20160321171738.GE6344@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <56F02B87.2000307@mellanox.com>
On Mon, Mar 21, 2016 at 01:12:39PM -0400, Chris Metcalf wrote:
> I do see mwait used in the ACPI 4.0 Processor Aggregator Device driver, but
> this seems sufficiently far removed from regular cpuidle that I don't
> think it's appropriate to tag the power_saving_thread() function -
> the initial commit talks about using the mechanism "to ride-out
> transient electrical and thermal emergencies."
>
> There's also the thermal "powerclamp" driver that enforces a particular
> amount of idle time across the system. For this one it's less clear to
> me whether this is a valid "idle" state that we should ignore when doing
> NMI backtracing. This would be the clamp_thread() function in
> drivers/thermal/intel_powerclamp.c. For now I'm not including it,
> but what do you think?
Both the acpi power aggregator and the powerclamp driver are forced idle
and have some serious issues, so are safe to ignore for now.
Also, I would explicitly not include them, because forced idle might
still be interesting.
> ># nm -n ivb-ep-build/vmlinux | awk '/__cpuidle_text_start/ {p=1} {if (p) print $0} /__cpuidle_text_end/ {p=0}'
> >ffffffff81b16ca8 T __cpuidle_text_start
> >ffffffff81b16cb0 T default_idle
> >ffffffff81b16e50 t mwait_idle
> >ffffffff81b17080 t cpu_idle_poll
> >ffffffff81b17280 T default_idle_call
> >ffffffff81b172be T __cpuidle_text_end
> >
> >So no intel_idle for me..
>
> With the changes discussed so far in this email thread, we've gotten to:
>
> ffffffff818df178 T __cpuidle_text_start
> ffffffff818df180 T default_idle
> ffffffff818df260 t mwait_idle
> ffffffff818df3f0 T acpi_processor_ffh_cstate_enter
> ffffffff818df4a0 T default_idle_call
> ffffffff818df4e0 t cpu_idle_poll
> ffffffff818df600 t intel_idle_freeze
You can skip this one, that only happens when you suspend to idle.
> ffffffff818df6a0 t intel_idle
> ffffffff818df7b5 T __cpuidle_text_end
>
> This is about 1,600 bytes (or about 450 instructions) that will cause
> NMI to skip doing a backtrace if the PC is anywhere in the range.
Yeah, the alternative is making mwait_idle_with_hints an actual
function, but then we get to somehow exclude the other users like the
forced idle stuff.
WARNING: multiple messages have this Message-ID (diff)
From: peterz@infradead.org (Peter Zijlstra)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 4/4] nmi_backtrace: generate one-line reports for idle cpus
Date: Mon, 21 Mar 2016 18:17:38 +0100 [thread overview]
Message-ID: <20160321171738.GE6344@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <56F02B87.2000307@mellanox.com>
On Mon, Mar 21, 2016 at 01:12:39PM -0400, Chris Metcalf wrote:
> I do see mwait used in the ACPI 4.0 Processor Aggregator Device driver, but
> this seems sufficiently far removed from regular cpuidle that I don't
> think it's appropriate to tag the power_saving_thread() function -
> the initial commit talks about using the mechanism "to ride-out
> transient electrical and thermal emergencies."
>
> There's also the thermal "powerclamp" driver that enforces a particular
> amount of idle time across the system. For this one it's less clear to
> me whether this is a valid "idle" state that we should ignore when doing
> NMI backtracing. This would be the clamp_thread() function in
> drivers/thermal/intel_powerclamp.c. For now I'm not including it,
> but what do you think?
Both the acpi power aggregator and the powerclamp driver are forced idle
and have some serious issues, so are safe to ignore for now.
Also, I would explicitly not include them, because forced idle might
still be interesting.
> ># nm -n ivb-ep-build/vmlinux | awk '/__cpuidle_text_start/ {p=1} {if (p) print $0} /__cpuidle_text_end/ {p=0}'
> >ffffffff81b16ca8 T __cpuidle_text_start
> >ffffffff81b16cb0 T default_idle
> >ffffffff81b16e50 t mwait_idle
> >ffffffff81b17080 t cpu_idle_poll
> >ffffffff81b17280 T default_idle_call
> >ffffffff81b172be T __cpuidle_text_end
> >
> >So no intel_idle for me..
>
> With the changes discussed so far in this email thread, we've gotten to:
>
> ffffffff818df178 T __cpuidle_text_start
> ffffffff818df180 T default_idle
> ffffffff818df260 t mwait_idle
> ffffffff818df3f0 T acpi_processor_ffh_cstate_enter
> ffffffff818df4a0 T default_idle_call
> ffffffff818df4e0 t cpu_idle_poll
> ffffffff818df600 t intel_idle_freeze
You can skip this one, that only happens when you suspend to idle.
> ffffffff818df6a0 t intel_idle
> ffffffff818df7b5 T __cpuidle_text_end
>
> This is about 1,600 bytes (or about 450 instructions) that will cause
> NMI to skip doing a backtrace if the PC is anywhere in the range.
Yeah, the alternative is making mwait_idle_with_hints an actual
function, but then we get to somehow exclude the other users like the
forced idle stuff.
next prev parent reply other threads:[~2016-03-21 17:17 UTC|newest]
Thread overview: 121+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-29 21:40 [PATCH 0/4] improvements to the nmi_backtrace code Chris Metcalf
2016-02-29 21:40 ` Chris Metcalf
2016-02-29 21:40 ` [PATCH 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods Chris Metcalf
2016-02-29 21:40 ` Chris Metcalf
2016-02-29 21:40 ` [PATCH 2/4] nmi_backtrace: generate one-line reports for idle cpus Chris Metcalf
2016-03-01 14:23 ` Daniel Thompson
2016-03-01 16:01 ` Chris Metcalf
2016-03-07 8:26 ` Daniel Thompson
2016-03-07 17:05 ` Chris Metcalf
2016-03-07 9:48 ` Peter Zijlstra
2016-03-07 17:38 ` Chris Metcalf
2016-03-07 20:43 ` Peter Zijlstra
2016-03-16 17:02 ` [PATCH v2 0/4] improvements to the nmi_backtrace code Chris Metcalf
2016-03-16 17:02 ` Chris Metcalf
2016-03-16 17:02 ` Chris Metcalf
2016-03-16 17:02 ` Chris Metcalf
2016-03-16 17:02 ` [PATCH v2 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods Chris Metcalf
2016-03-16 17:02 ` Chris Metcalf
2016-03-17 19:36 ` Peter Zijlstra
2016-03-17 19:36 ` Peter Zijlstra
2016-03-17 22:31 ` Chris Metcalf
2016-03-17 22:31 ` Chris Metcalf
2016-03-17 22:38 ` Peter Zijlstra
2016-03-17 22:38 ` Peter Zijlstra
2016-03-17 22:41 ` Chris Metcalf
2016-03-17 22:41 ` Chris Metcalf
2016-03-17 23:14 ` Peter Zijlstra
2016-03-17 23:14 ` Peter Zijlstra
2016-03-17 22:55 ` Paul E. McKenney
2016-03-17 22:55 ` Paul E. McKenney
2016-03-17 23:09 ` Peter Zijlstra
2016-03-17 23:09 ` Peter Zijlstra
2016-03-17 23:11 ` Peter Zijlstra
2016-03-17 23:11 ` Peter Zijlstra
2016-03-18 0:28 ` Paul E. McKenney
2016-03-18 0:28 ` Paul E. McKenney
2016-03-18 0:17 ` Chris Metcalf
2016-03-18 0:17 ` Chris Metcalf
2016-03-18 0:33 ` Paul E. McKenney
2016-03-18 0:33 ` Paul E. McKenney
2016-03-18 9:40 ` Daniel Thompson
2016-03-18 9:40 ` Daniel Thompson
2016-03-18 23:54 ` Paul E. McKenney
2016-03-18 23:54 ` Paul E. McKenney
2016-03-16 17:02 ` [PATCH v2 2/4] nmi_backtrace: do a local dump_stack() instead of a self-NMI Chris Metcalf
2016-03-16 17:02 ` Chris Metcalf
2016-03-16 17:02 ` [PATCH v2 3/4] arch/tile: adopt the new nmi_backtrace framework Chris Metcalf
2016-03-16 17:02 ` [PATCH v2 4/4] nmi_backtrace: generate one-line reports for idle cpus Chris Metcalf
2016-03-16 17:02 ` Chris Metcalf
2016-03-16 17:02 ` Chris Metcalf
2016-03-16 18:46 ` kbuild test robot
2016-03-16 18:46 ` kbuild test robot
2016-03-16 18:46 ` kbuild test robot
2016-03-16 18:46 ` kbuild test robot
2016-03-21 15:38 ` Peter Zijlstra
2016-03-21 15:38 ` Peter Zijlstra
2016-03-21 15:38 ` Peter Zijlstra
2016-03-21 15:46 ` Chris Metcalf
2016-03-21 15:46 ` Chris Metcalf
2016-03-21 15:46 ` Chris Metcalf
2016-03-21 15:46 ` Chris Metcalf
2016-03-21 15:42 ` Peter Zijlstra
2016-03-21 15:42 ` Peter Zijlstra
2016-03-21 16:15 ` Chris Metcalf
2016-03-21 16:15 ` Chris Metcalf
2016-03-21 16:15 ` Chris Metcalf
2016-03-21 16:32 ` Peter Zijlstra
2016-03-21 16:32 ` Peter Zijlstra
2016-03-21 17:12 ` Chris Metcalf
2016-03-21 17:12 ` Chris Metcalf
2016-03-21 17:12 ` Chris Metcalf
2016-03-21 17:12 ` Chris Metcalf
2016-03-21 17:17 ` Peter Zijlstra [this message]
2016-03-21 17:17 ` Peter Zijlstra
2016-03-21 16:48 ` Peter Zijlstra
2016-03-21 16:48 ` Peter Zijlstra
2016-03-21 21:49 ` Peter Zijlstra
2016-03-21 21:49 ` Peter Zijlstra
2016-03-22 17:19 ` [PATCH v3 0/4] improvements to the nmi_backtrace code Chris Metcalf
2016-03-22 17:19 ` Chris Metcalf
2016-03-22 17:19 ` Chris Metcalf
2016-03-22 17:19 ` Chris Metcalf
2016-03-22 17:19 ` [PATCH v3 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods Chris Metcalf
2016-03-22 17:19 ` Chris Metcalf
2016-03-22 17:19 ` [PATCH v3 2/4] nmi_backtrace: do a local dump_stack() instead of a self-NMI Chris Metcalf
2016-03-22 17:19 ` Chris Metcalf
2016-03-22 17:19 ` [PATCH v3 3/4] arch/tile: adopt the new nmi_backtrace framework Chris Metcalf
2016-03-22 17:19 ` [PATCH v3 4/4] nmi_backtrace: generate one-line reports for idle cpus Chris Metcalf
2016-03-22 17:19 ` Chris Metcalf
2016-03-22 17:19 ` Chris Metcalf
2016-03-22 17:30 ` Peter Zijlstra
2016-03-22 17:30 ` Peter Zijlstra
2016-03-22 22:28 ` Rafael J. Wysocki
2016-03-22 22:28 ` Rafael J. Wysocki
2016-03-22 22:31 ` Rafael J. Wysocki
2016-03-22 22:31 ` Rafael J. Wysocki
2016-03-22 22:45 ` Peter Zijlstra
2016-03-22 22:45 ` Peter Zijlstra
2016-03-23 0:50 ` Rafael J. Wysocki
2016-03-23 0:50 ` Rafael J. Wysocki
2016-03-23 7:53 ` Peter Zijlstra
2016-03-23 7:53 ` Peter Zijlstra
2016-03-30 17:16 ` [PATCH v4 0/4] improvements to the nmi_backtrace code Chris Metcalf
2016-03-30 17:16 ` Chris Metcalf
2016-03-30 17:16 ` Chris Metcalf
2016-03-30 17:16 ` Chris Metcalf
2016-03-30 17:16 ` [PATCH v4 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods Chris Metcalf
2016-03-30 17:16 ` Chris Metcalf
2016-03-30 17:16 ` [PATCH v4 2/4] nmi_backtrace: do a local dump_stack() instead of a self-NMI Chris Metcalf
2016-03-30 17:16 ` Chris Metcalf
2016-03-30 17:16 ` [PATCH v4 3/4] arch/tile: adopt the new nmi_backtrace framework Chris Metcalf
2016-03-30 17:16 ` [PATCH v4 4/4] nmi_backtrace: generate one-line reports for idle cpus Chris Metcalf
2016-03-30 17:16 ` Chris Metcalf
2016-03-30 17:16 ` Chris Metcalf
2016-02-29 21:40 ` [PATCH 3/4] nmi_backtrace: do a local dump_stack() instead of a self-NMI Chris Metcalf
2016-02-29 21:40 ` Chris Metcalf
2016-02-29 21:40 ` [PATCH 4/4] arch/tile: adopt the new nmi_backtrace framework Chris Metcalf
2016-03-01 0:49 ` [PATCH 0/4] improvements to the nmi_backtrace code Andrew Morton
2016-03-01 0:49 ` Andrew Morton
2016-03-01 10:01 ` Petr Mladek
2016-03-01 10:01 ` Petr Mladek
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