Re: [PATCH 3/3] nvme: Enable autonomous power state transitions

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/3] nvme: Enable autonomous power state transitions
Date	2016-09-02 21:00 +0200
Message-ID	<sd1R0-39s-5@gated-at.bofh.it> (permalink)
References	(1 earlier) <sbr3b-5vm-3@gated-at.bofh.it> <sbwme-rU-19@gated-at.bofh.it> <sbE0p-5h6-7@gated-at.bofh.it> <sbXPr-1hr-9@gated-at.bofh.it> <sd1ei-2Tg-31@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Fri, Sep 2, 2016 at 11:11 AM, J Freyensee
<james_p_freyensee@linux.intel.com> wrote:
>
>> > >
>> > >
>> > > >
>> > > > +     /*
>> > > > +      * By default, allow up to 25ms of APST-induced
>> > > > latency.  This will
>> > > > +      * have no effect on non-APST supporting controllers
>> > > > (i.e.
>> > > > any
>> > > > +      * controller with APSTA == 0).
>> > > > +      */
>> > > > +     ctrl->apst_max_latency_ns = 25000000;
>> > >
>> > > Is it possible to make that a #define please?
>> >
>> > I'll make it a module parameter as Keith suggested.
>>
>> One question, though: should we call this and the sysfs parameter
>> apst_max_latency or should it be more generically
>> power_save_max_latency?  The idea is that we might want to support
>> non-automonous transitions some day or even runtime D3.  Or maybe
>> those should be separately configured if used.
>
> I read the spec and reviewed your latest patchset.  Personally for me I
> like having the field names from the NVMe spec in the names of the
> Linux implementation because it makes it easier to find and relate the
> two.  So apst_max_latency makes more sense to me, as this is a
> 'apst'(e/a) NVMe feature.
>

It's not really an APST feature, though -- it's just the maximum
(entry + exit) latency from the power state table.  So if we every
supported non-APST power state transitions, we could use the same type
of policy.

I'm not really arguing for changing it, though, and I personally have
no plans to implement a non-autonomous policy.

--Andy

Thread

[PATCH 3/3] nvme: Enable autonomous power state transitions Andy Lutomirski <luto@kernel.org> - 2016-08-29 11:30 +0200
  Re: [PATCH 3/3] nvme: Enable autonomous power state transitions J Freyensee <james_p_freyensee@linux.intel.com> - 2016-08-29 17:10 +0200
    Re: [PATCH 3/3] nvme: Enable autonomous power state transitions Andy Lutomirski <luto@amacapital.net> - 2016-08-30 01:20 +0200
      Re: [PATCH 3/3] nvme: Enable autonomous power state transitions Andy Lutomirski <luto@amacapital.net> - 2016-08-30 22:30 +0200
        Re: [PATCH 3/3] nvme: Enable autonomous power state transitions J Freyensee <james_p_freyensee@linux.intel.com> - 2016-09-02 20:20 +0200
          Re: [PATCH 3/3] nvme: Enable autonomous power state transitions Andy Lutomirski <luto@amacapital.net> - 2016-09-02 21:00 +0200
  Re: [PATCH 3/3] nvme: Enable autonomous power state transitions Keith Busch <keith.busch@intel.com> - 2016-08-29 18:40 +0200
    Re: [PATCH 3/3] nvme: Enable autonomous power state transitions Andy Lutomirski <luto@amacapital.net> - 2016-08-30 01:20 +0200

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