Message-ID: <1372111148.3944.161.camel@pasglop>
Subject: Re: power-efficient scheduling design
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        David Lang <david@lang.hm>,
        "len.brown@intel.com" <len.brown@intel.com>,
        "alex.shi@intel.com" <alex.shi@intel.com>,
        "corbet@lwn.net" <corbet@lwn.net>,
        "peterz@infradead.org" <peterz@infradead.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "efault@gmx.de" <efault@gmx.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linaro-kernel@lists.linaro.org" <linaro-kernel@lists.linaro.org>,
        "preeti@linux.vnet.ibm.com" <preeti@linux.vnet.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "pjt@google.com" <pjt@google.com>, Ingo Molnar <mingo@kernel.org>
Date: Tue, 25 Jun 2013 07:59:08 +1000
In-Reply-To: <51C8651D.4010607@linux.intel.com>
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On Mon, 2013-06-24 at 08:26 -0700, Arjan van de Ven wrote:
> 
> to bring the system back up if all cores in the whole system are idle and power gated,
> memory in SR etc... is typically < 250 usec (depends on the exact version
> of the cpu etc). But the moment even one core is running, that core will keep the system
> out of such deep state, and waking up a consecutive entity is much faster
> 
> to bring just a core out of power gating is more in the 40 to 50 usec range

Out of curiosity, what happens to PCIe when you bring a package down
like this ?

Cheers,
Ben.


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