From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johan Hovold Subject: Re: Performance regression in v3.14 Date: Wed, 28 May 2014 09:59:45 +0200 Message-ID: <20140528075945.GA21705@localhost> References: <20140506163559.GA5308@localhost> <536A3EE9.5050409@intel.com> <20140521090051.GO21412@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20140521090051.GO21412@localhost> Sender: cpufreq-owner@vger.kernel.org To: Dirk Brandewie Cc: Viresh Kumar , Johan Hovold , dirk.j.brandewie@intel.com, "Rafael J. Wysocki" , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List , Greg Kroah-Hartman , Doug Smythies , Yuyang Du , Stratos Karafotis List-Id: linux-pm@vger.kernel.org [ +CC: Greg, Doug, Stratos, Yuyang ] On Wed, May 21, 2014 at 11:00:51AM +0200, Johan Hovold wrote: > On Wed, May 07, 2014 at 07:10:49AM -0700, Dirk Brandewie wrote: > > On 05/06/2014 10:40 PM, Viresh Kumar wrote: > > > Cc'ing Dirk who is taking care of intel-pstate driver. > > > > > > > Thanks Viresh I had seen this thread. > > > > I am looking into it > > Any updates on this, Dirk? 3.14 is still basically unusable with the > intel_pstate driver. > > Any fixes or workarounds posted elsewhere that I can apply in the > meantime? Another week and still no reply, Dirk? I tried applying your (rejected) patch "intel_pstate: Remove C0 tracking" posted here: https://lkml.org/lkml/2014/5/8/574 to v3.14.4 and it fixes the problem as expected. So we have a commit fcb6a15c2e7e ("intel_pstate: Take core C0 time into account for core busy calculation") that went into v3.14-rc2 (and was even marked for *stable*) that first broke Greg KH's system: https://lkml.org/lkml/2014/2/19/626 That was apparently fixed by e66c17683746 ("intel_pstate: Change busy calculation to use fixed point math."), but still left v3.14 basically unusable for lower-intensity workloads such as my bash-completion example and other reported regressions: https://bugzilla.kernel.org/show_bug.cgi?id=75121 Sure there may be issues with v3.13 not hitting the lowest frequencies but at least the system was *usable*. In my opinion there's really no other option than to restore the 3.13 behaviour by effectively reverting fcb6a15c2e7e ("intel_pstate: Take core C0 time into account for core busy calculation") until you have figured out a way to take C0 into account without breaking things too badly. Johan