Thus spake Len Brown (lenb@xxxxxxxxxx): > On Tuesday 23 January 2007 16:00, Henrique de Moraes Holschuh wrote: > > On Tue, 23 Jan 2007, Mike Perry wrote: > > > Is there currently any way to disable busmastering or C3 transitions > > > (without recompilation)? Or better: is it possible to make the system > > > less eager to transition into C3 or otherwise reduce the frequency of > > > these transitions? If I could just get the frequency of transitions to > > > get out of the audible range, my life would be a lot better. > > > > Read http://thinkwiki.org/wiki/Problem_with_high_pitch_noises, it may have > > the answers. > > Pretty good write-up. It is correct, you should try max_cstate. > > for n starting at 3 and decreasing until the stound stops: > # echo n > /sys/module/processor/parameters/max_cstate Ahh, very nice. The whine stops at n=2, which is consistent with my hack of manually disabling busmastering (which kills C3). At least now I have the option of peace and quiet vs longer battery life+annoying whine. Probably a tolerable option for plane flights :) > BTW. what model Thinkpad do you have? I actually have a Compaq Presario V6000T (Intel version). I was afraid to mention it because Compaqs are historically pretty junky and I figured someone would just say "that's what you get for buying junk" :) But aside from the whine the machine is really nice (slim form factor, very light yet durable, standard components, etc). ACPI suspend to RAM and such is also fully functional (at least with the Fedora kernels). > On some older systems, this pops all the way to C0, and on newer > systems it transparently pops to C2 and returns to C3 w/o waking the > OS. You can get rid of it by disabling USB. But it sounds like in > the full-on case you've got an issue even with USB disabled. Or > sometimes you can bias the system to simply not enter C3 if it sees > bus master traffic with > > # echo 0xFFFFFFFF > /sys/module/processor/parameters/bm_history Yeah, unfortunately this has no effect, even if I enable CONFIG_HZ=100 and CONFIG_HZ_100. What about that suspicious threshold structure in the acpi_processor_cx struct? Is there any reasoning behind these magic numbers in there for each state? > Another thing to try building the kernel with CONFIG_HZ=100 -- which > is what a kernel for most laptops should be using in the first place. As an aside, maybe this config option should be moved to a boot parameter? I don't think you're going to see distros shipping laptop kernels vs desktop kernels anytime soon.. But it doesn't seem to make any difference for me either way. -- Mike Perry Mad Computer Scientist fscked.org evil labs - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
