From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Renninger Subject: Re: Overall picture of cpufreq.. Date: Mon, 14 Jan 2008 10:51:50 +0100 Message-ID: <1200304310.23376.311.camel@queen.suse.de> References: <9f79f7f50801111415w354dc91fwfeec98b16a00fb74@mail.gmail.com> <1200264884.4157.16.camel@queen> <9f79f7f50801131812x6a68c202tb4c25fa2116b32e4@mail.gmail.com> <478B0A82.6050503@wpkg.org> Reply-To: trenn@suse.de Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <478B0A82.6050503@wpkg.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: cpufreq-bounces@lists.linux.org.uk Errors-To: cpufreq-bounces+glkc-cpufreq=m.gmane.org+glkc-cpufreq=m.gmane.org@lists.linux.org.uk To: Tomasz Chmielewski Cc: Martin.Leisner@xerox.com, cpufreq@lists.linux.org.uk On Mon, 2008-01-14 at 08:08 +0100, Tomasz Chmielewski wrote: > Saru Addep schrieb: > > Hi Thomas, > > > > So that means if we have an ondemand governor properly instrumented, there > > is no need to have userspace governor. In the case of ondemand governor, the > > only work that will be left to userspace would be to set the min, and max > > freq. The complete intelligence of DVFS algoritm is present inside the > > ondemand governor. Is my understanding correct. Yes, this is correct. > It looks to me that ondemand governor doesn't have "the complete > intelligence". > > For example, it doesn't detect CPU load coming from some kernel tasks, > like kcryptd: reads/writes from a device crypted with dm-crypt will be > very slow if one uses the ondemand governor, as CPU speed will always be > set to the lowest possible (so there is not enough power to > crypt/decrypt data). > > Ironically, this is the only case when starting bzip2 will speed up your > disk access... Or, use a userspace governor. > > > See also http://bugzilla.kernel.org/show_bug.cgi?id=9729 I don't know about this one. AFAIK there has been some work done there, I expect the bug in the crypto area, not in cpufreq/ondemand layer. A Xeon processor stepped down from 2800 to 350 looks bogus (maybe the new ones even can, not sure), could it be that you are using p4-clockmode driver which is doing throttling, not frequency scaling, better try with acpi-cpufreq then. Thomas