From: Mark Lord <lkml@rtr.ca>
To: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
abelay@novell.com, lenb@kernel.org, mlord@pobox.com, rjw@sisk.pl,
linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org
Subject: Re: + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree
Date: Fri, 30 Nov 2007 21:52:40 -0500 [thread overview]
Message-ID: <4750CC78.9070105@rtr.ca> (raw)
In-Reply-To: <924EFEDD5F540B4284297C4DC59F3DEE2FAEAF@orsmsx423.amr.corp.intel.com>
Pallipadi, Venkatesh wrote:
>
>
>> On Fri, 30 Nov 2007 14:06:55 -0800
>> "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com> wrote:
>>
>> Please dont go off-list like this. I put Mark's original
>> mailing list cc's
>> back.
>
> Sorry for missing some cc's earlier. I blindly did a reply-all to the
> mm-commits mail I got.
>
>>> I will have to Nack this. The reason max_cstate was initentionally
>>> removed due to couple of reasons:
>> It broke userspace without any warning or migration period, afaict.
>
> Yes. That's true. I will have to take the blame for that. It has been
> known for a while during cpuidle development. But, it was never
> documented as deprecating.
>
>>> 1) All in kernel users of max_cstate should rather be using
>>> pm_qos/latency interfaces. All such max_cstate usages must already be
>>> migrated.
>> That code isn't merged.
>
> All kernel part is already merged. I mean, there are do drivers that
> depend on max_cstate. They use latency_notifier thing today and their
> migration to pm_qos part is not merged yet.
>
>>> 2) Supporting max_cstate as a dynamic parameter cleanly is no longer
>>> possible in acpi/processor_idle.c as the C-state policy has moved to
>>> cpuidle instead. It can be done if it is needed. But, just
>> below patch
>>> will not really work with cpuidle.
>>>
>>> Selecting max_cstate at boot time as a debug option still
>> works without
>>> this patch.
>>>
>>> So, just this patch will not get back the functionality with cpuidle.
>>> Infact changing it at run time will have no effect. Question
>> however is:
>>> Is there a real need to revive this parameter so that user can change
>>> max_cstate at run time?
>> It is not known whether Mark is actually writing to this
>> thing. Perhaps
>> read-only permissions would be a suitable fix?
>>
>
> Exporting it as read only should be OK. We also need to know if there
> are hard user space dependency on writing to this from userspace.
..
Well, actually.. my scripts have a firm need to write "1" to it,
and then later restore the original value.
This is needed to *greatly* speed up an otherwise sluggish binary I use,
as well as whenever I want to semi-accurately benchmark I/O.
Is there another way to achieve exactly the same behaviour?
Thanks
next prev parent reply other threads:[~2007-12-01 2:52 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200711302153.lAULrZ7n026255@imap1.linux-foundation.org>
[not found] ` <924EFEDD5F540B4284297C4DC59F3DEE2FAE6A@orsmsx423.amr.corp.intel.com>
2007-11-30 22:20 ` + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree Andrew Morton
2007-11-30 22:37 ` Pallipadi, Venkatesh
2007-12-01 2:52 ` Mark Lord [this message]
2007-12-01 3:02 ` Arjan van de Ven
2007-12-01 3:14 ` Mark Lord
2007-12-01 3:18 ` Arjan van de Ven
2007-12-01 3:31 ` Mark Lord
2007-12-01 3:44 ` Mark Lord
2007-12-01 3:48 ` Mark Lord
2007-12-01 4:02 ` Mark Lord
2007-12-01 4:31 ` Mark Lord
2007-12-01 23:43 ` 20000+ wake-ups/second in 2.6.24. Bug? Mark Lord
2007-12-01 23:46 ` Arjan van de Ven
2007-12-01 23:55 ` Mark Lord
2007-12-02 0:13 ` Arjan van de Ven
2007-12-02 1:10 ` Andres Freund
2007-12-02 0:20 ` Rafael J. Wysocki
2008-02-04 17:29 ` Mark Lord
2008-02-04 17:50 ` Arjan van de Ven
2008-02-04 19:17 ` Mark Lord
2007-12-02 14:41 ` Adrian Bunk
2007-12-02 14:59 ` Mark Lord
2007-12-02 15:12 ` Adrian Bunk
2007-12-02 15:45 ` Mark Lord
2007-12-02 15:45 ` Mark Lord
2007-12-02 15:49 ` Mark Lord
2008-01-02 23:41 ` + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree Mark Lord
2008-01-03 0:06 ` Pallipadi, Venkatesh
2008-01-03 0:51 ` Andrew Morton
2008-01-03 1:12 ` Pallipadi, Venkatesh
2008-01-03 4:25 ` Mark Lord
2008-01-03 4:18 ` Mark Lord
2008-01-04 2:16 ` Venki Pallipadi
2008-01-04 3:16 ` Mark Lord
2008-01-04 21:52 ` Mark Lord
2008-01-04 21:59 ` Pallipadi, Venkatesh
2008-01-05 16:27 ` Mark Lord
2008-01-06 21:34 ` Mark Lord
2008-01-07 7:18 ` Andrew Morton
2008-01-07 14:07 ` Arjan van de Ven
2008-01-07 15:07 ` Mark Lord
2008-01-07 14:18 ` Pallipadi, Venkatesh
2008-01-07 15:06 ` Mark Lord
2008-01-07 19:12 ` Len Brown
2008-01-07 21:33 ` Mark Lord
2008-01-07 22:43 ` Len Brown
2007-12-01 10:17 ` Andrew Morton
2007-12-01 16:30 ` Arjan van de Ven
2007-12-05 11:17 ` Pavel Machek
2007-12-07 21:38 ` Pallipadi, Venkatesh
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