Messages in this thread | | | From | Andrew Lutomirski <> | Date | Fri, 2 Dec 2011 10:34:55 -0800 | Subject | Re: i915: RC6 causes sudden shutdowns |
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On Thu, Dec 1, 2011 at 9:00 PM, Patrik Kullman <patrik.kullman@gmail.com> wrote: > 2011/12/1 Andy Lutomirski <luto@mit.edu>: >> On 11/23/2011 03:43 PM, Patrik Kullman wrote: >>> Hi, >>> >>> I recently acquired the Asus Zenbook UX31E but have been looking for >>> ways to extend the battery life. >>> >>> I read that the i915_enable_rc6 parameter could decrease power usage >>> significantly and tried it with the 3.1.1 and 3.1.2 kernels, and >>> indeed it does. >>> However, I (and the other Zenbook-owners from the Ubuntu forums) >>> experience sudden, unexpected shutdowns (for me, 1-4 times per day) >>> with this parameter. >>> It's as sudden as a power loss. >> >> Do you have DMAR enabled? If so, it's a known problem and it's being >> worked on (and the default will not change for you AFAICT). If not, you >> should send a bug report to the intel-gfx -- several people there care >> about this. >> >> --Andy > > Well, it's not something I've explicitly enabled. > > Is it on by default?
Depends on config options. You can probably get a good idea by looking for "DMAR" in your kernel log.
> > If so, any reason why I wouldn't want to disable it?
There are three reasons to enable it:
1. If you're paranoid and want to (partially) protect your system against malicious PCI/PCIe cards. 2. If you assign devices in your system to VM guests. 3. If you have more than 4GB of RAM and you have DMA-capable devices that can only address 32 bits, then you might get a performance boost.
In other words, for normal desktop use, you don't need it. Try booting with intel_iommu=off.
--Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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