From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dominik Brodowski Subject: Re: [PATCH] 3/3 Dynamic cpufreq governor and updates to ACPIP-state driver Date: Tue, 21 Oct 2003 22:39:00 +0200 Sender: cpufreq-bounces@www.linux.org.uk Message-ID: <20031021203900.GG26971@brodo.de> References: <7F740D512C7C1046AB53446D3720017304B031@scsmsx402.sc.intel.com> <1066766155.a66ff46274f08@carlthompson.net> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <1066766155.a66ff46274f08@carlthompson.net> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: cpufreq-bounces@www.linux.org.uk Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Carl Thompson Cc: cpufreq@www.linux.org.uk, "Nakajima, Jun" , "Pallipadi, Venkatesh" , "Mallick, Asit K" , arjanv@redhat.com, linux-acpi On Tue, Oct 21, 2003 at 12:55:55PM -0700, Carl Thompson wrote: > Quoting "Nakajima, Jun" : > > > ... > > > It's about the frequency of the feedback loop. As we have much lower > > latency with P-state transitions, the sampling time can be order of > > millisecond (or shorter if meaningful). A userland daemon can have a > > high-level policy (preferences, or set of parameters), but it cannot be > > part of the real feedback loop. If we combine P-state transitions and > > deeper C-state transitions, the situation is worse with a userland > > daemon. > > You are making the assumption that a higher polling frequency (we'll say > 1ms) is in general better than a lower frequency (we'll say 1s). I submit > that it is not. > > If I hit a key on my keyboard and your high frequency loop increases CPU > speed so that my word processor displays the letter 0.01s faster, is that > really beneficial? If a window renders in 0.2s seconds instead of 0.3s is > that a difference I am going to notice? > > On the other hand, if I do a kernel compile and it is done 0.999s faster > with the higher frequency loop, am I going to miss that second over such a > long duration? (In reality, the compile with the high-frequency loop would > probably take longer unless it has near zero overhead). > > In my opinion it is wasteful to increase CPU speed unless there is a longer > term need for it. Different needs, different opinions, different governors... Dominik