linux-kernel - Re: [RFC] maximum latency tracking infrastructure

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Date:	Thu, 24 Aug 2006 14:08:03 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, len.brown@...el.com
Subject: Re: [RFC] maximum latency tracking infrastructure

On Thursday, August 24, 2006 10:41 am, Arjan van de Ven wrote:
> The reason for adding this infrastructure is that power management in
> the idle loop needs to make a tradeoff between latency and power
> savings (deeper power save modes have a longer latency to running code
> again).

What if a processor was already in a sleep state when a call to 
set_acceptable_latency() latency occurs?  Should there be a callback so 
they can be woken up?  A callback would also allow ACPI to tell the 
user "disabling C3 because of device <foo>" or somesuch, which might be 
nice.

Also, should subsystems have the ability to set a lower bound on  
latency?  That would mean set_acceptable_latency() could fail, 
indicating that the user should buy a better device or a system with 
better realtime guarantees, which is also valuable info.

Comments aside, this is a nice interface, should help clarify things for 
devices with response time limits.

Thanks,
Jesse
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