On Mon, 25 Oct 2010 13:11:24 -0700 Jesse Barnes <[email protected]> wrote:
> On Sat, 23 Oct 2010 13:02:35 +0100 > Peter Clifton <[email protected]> wrote: > > I think Keith was thinking that there are some parts of the chipset > > which are shared between the GPU and CPU (memory controllers?), and the > > CPU entering a lower frequency state could have a detrimental effect on > > the graphics throughput. > > > > I know in heavy workloads the CPU is likely to be "a bit" busy, and > > rendering will not be totally GPU bound, but it would seem like it is > > eventually necessary to have some hook to bump the CPU frequency (or > > chipset frequency?) when the GPU would make beneficial use of the extra > > throughput. > > > > This doesn't make sense if it is banging out 100fps, but for my stuff, > > the GPU is struggling to make 5fps for some complex circuit boards. I'm > > trying to address that from a geometry / rendering complexity point of > > view, but also, I'd love to see my laptop being able to get the best out > > of its hardware. > > > > Perhaps we need to account for periods when the CPU has tasks idle > > waiting for GPU operations which would be sped up by increasing some > > chip power state. > > > > I'm probably not up to coding this all, but if the idea sounds feasible, > > I'd love to know, so I might be able to have a tinker with it. > > There are some bits in the GMCH to control memory behavior during CPU > C-states. Can you dump the 16 bits at MCHBAR address 0xf08? You > should be able to do that by doing I915_READ16(MCHBAR_MIRROR_BASE + > 0xf08). Assuming bits 3:2 and 1:0 are nonzero, it may help to set them > all to 0. That will disable several memory related power saving > features while the CPU is in a deep sleep state. Oh and bits 5:4 and bit 6 as well. Bit 6 controls whether memory stays active in C2, and bits 5:4 control which memory shutdown features are enabled in C2; clearing 5:4 will disable shutdown, as will bit 6. -- Jesse Barnes, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
