From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Yu, Luming" Subject: RE: Processor C states and USB problem Date: Sun, 18 Jan 2004 11:17:38 +0800 Sender: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Message-ID: <3ACA40606221794F80A5670F0AF15F8401720CE2@PDSMSX403.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: content-class: urn:content-classes:message Errors-To: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Diego SANTA CRUZ Cc: acpi-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-acpi@vger.kernel.org >=20 > Yes, but compared to the usage count of C2 that is extremely low, and > the CPU is idling all the time (CPU usage is below 1%). I don't know > much about C states but I guess it should go into C3 much more often, > and the bus mastering activity should show something else=20 > than ffffffff > when booting with a bare bones kernel and with no extra hw initialized > (USB, FireWire, etc.) I agree that it's unreasonable that C3 usage count is never above 5.=20 This is the result of the C state power policy.=20 Threshold is: pr->power.states[ACPI_STATE_C2].promotion.threshold.bm =3D 0x0F; pr->power.states[ACPI_STATE_C3].demotion.threshold.bm =3D 0x0F; The condition of promotion or demotion is: if (pr->power.bm_activity & cx->demotion.threshold.bm) { if (!(pr->power.bm_activity & cx->promotion.threshold.bm)) { Using the following statement to adjust bm_activity of the last Nth schedule quanta. pr->power.bm_activity <<=3D 1; if(bm_status) pr->power.bm_activity++; So it's is not strange that C3 usage count is 4 ! Maybe we need a more sophisticated policy . ------------------------------------------------------- The SF.Net email is sponsored by EclipseCon 2004 Premiere Conference on Open Tools Development and Integration See the breadth of Eclipse activity. February 3-5 in Anaheim, CA. http://www.eclipsecon.org/osdn